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Browse our collection of Technical Notes written by some of our in-house experts.
These are more in-depth explanations for our most frequently asked questions. For a quick topic answer, visit our Technical Support section.
 | Cleaning Your Optical Filters - Because Semrock manufactures only hard coated filters, you may handle, install and even clean your filters without fear of damage. | | Working with Optical Density - Optical Density (OD) is a convenient tool to describe the transmission of light through a highly blocking optical filter (when the transmission is extremely small). | | 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. | | What is Pixel Shift? - Pixel shift results when a filter in an imaging path with a non-zero wedge angle deviates the light rays to cause a shift of the image detected on a high-resolution CCD camera. Combining images from multiple filter sets to build a multicolor image can create an inaccurate representation this wedge angle is not eliminated. | | 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. | | 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°. |
| Cube Assembly Instructions - Semrock offers free assembly service if you send in your microscope cube when purchasing new filter sets, but for those do-it-yourselfers we give you the downloadable PDF files that show you step-by-step how to populate and assemble your own popular cube models. | | Flatness of Dichroic Beamsplitters - Glass substrate is not always perfectly flat, especially after it is coated, since the intrinsic stress of hard glass coatings can cause slight bending of the substrate. This bending can cause focal plane shift and image distortion when imaging reflected light. | | Introduction to Fluorescence Filters - Optical fluorescence occurs when a molecule absorbs light at wavelengths within its absorption band, and then nearly instantaneously emits light at longer wavelengths within its emission band. Fluorescence microscopes use three basic filters to view this fluorescence: an excitation filter (or exciter), a dichroic beamsplitter (or dichromatic mirror), and an emission filter (or barrier filter). | | Multiband Filter Set Terminology - To satisfy the ever-increasing demand for high-speed imaging, especially for live-cell real-time analysis using fluorescent protein labels, there is a need for an alternative to the single-band filter cube approach without sacrificing image fidelity. | | Ultraviolet Fluorescence Applications - Many biological molecules of interest naturally fluoresce when excited by shorter- wavelength UV light. Because the fluorescence is intrinsic, samples can be observed without the added chemistry and limitations associated with "indirect" labeling by extrinsic fluorophores. | | Fluorescence Resonance Energy Transfer - Fluorescence Resonance Energy Transfer (FRET) is a powerful technique for characterizing distance-dependent interactions on a molecular scale. It is one of the few tools available that is able to measure intermolecular and intramolecular distance interactions both in-vivo and in-vitro. | | Using Fura-2 to Track Ca2+ - The fluorophore Fura-2 has an absorption spectrum that varies markedly depending on the concentration of calcium (Ca2+) that is present near the fluorophore molecule. | | Tunable Bandpass Filters - Semrock has now developed a revolutionary new optical filter technology: thin-film filters that are tunable over a wide range of wavelengths by adjusting the angle of incidence with essentially no change in spectral performance. | | BrightLine Multiphoton Fluorescence Filters - The advantages offered by multiphoton imaging systems include true three-dimensional imaging, the ability to image deep inside of live tissue and the elimination of out-of-plane fluorescence. | | Fluorescence Imaging with Quantum Dot Nanocrystals - Quantum dot nanocrystals are fluorophores in that they absorb photons of light and then re-emit longer-wavelength photons, however, there are some important differences between quantum dots and traditional fluorophores. | | Optical Filters for Laser-based Fluorescence Microscopes - The advent of lasers as light sources for fluorescence imaging imposes new constraints on imaging systems and their components. | | Optical Filter Configurations for FRET - Explanations of the classic and most popular approaches to the FRET method of imaging. | | Spectral Imaging with VersaChrome Filters - Using tunable bandpass filters in spectral imaging systems in a range of applications. | | Using Fura-2 to Track Calcium Using VersaChrome Filters - Ratiometric imaging with Fura-2 can be more carefully optimized to your specific experimental conditions when using tunable bandpass filters. |
| Edge Filters vs. Notch Filters for Raman Instrumentation - Compares the benefits and drawbacks of different Raman instrumentation layouts. | | Filter Types for Raman Spectroscopy Applications - Raman spectroscopy, an intense laser beam is used to excite a sample and the Raman "finger print" is measured by a dispersive or Fourier Transform spectrometer. Optical filters are used to prevent the undesired light from reaching the spectrometer and drowning out the relatively weak Raman signal. | | RazorEdge Filter Layouts - They layout of your Raman system will determine which optical filters are needed. | | Transition Width & Edge Steepness - Transition width and edge steepness are two terms often used to describe the spectral properties of edge filters and it is important to know that these two terms are related, but not interchangeable. | | Ultraviolet (UV) Raman Spectroscopy - Measuring Raman spectra in the ultraviolet (UV) wavelength range has significant benefits over traditional Raman measurements performed with green, red, or near-infrared (IR) lasers. | | Laser Damage Threshold - Laser damage to optical filters is strongly dependent on many factors, including laser type, power and beam diameter. | | Optical Filters for Laser-based Fluorescence Microscopes - The advent of lasers as light sources for fluorescence imaging imposes new constraints on imaging systems and their components. | | BrightLine Multiphoton Fluorescence Filters - The advantages offered by multiphoton imaging systems include true three-dimensional imaging, the ability to image deep inside of live tissue and the elimination of out-of-plane fluorescence. | | Group Delay Dispersion (GDD) for Reflected Laser Light - Pulse broadening is caused by dispersion associated with the optics used to direct and focus the laser light onto the sample, including mirrors, lenses, and beamsplitters. It is always desirable to keep the dispersion of these components to a minimum. |
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