Light is central to our existence, from the process of photosynthesis which generates much of our food to illuminating our homes. But some of its most fascinating applications are in industrial and scientific applications. Various methods of modifying the spectral properties of light drive everything from commercial photography and security to weapons guidance, space exploration, spectroscopy, and more.
Optical filters represent one of the key components used in altering the properties of light. Using glass (or sometimes plastic) as a substrate, optical filters are made by assembling thin films of materials that affect light — how much is absorbed, reflected or transmitted, its polarization, or otherwise changing it for its intended purpose. If you’re not sure which optical filter best suits the needs of your business, look no further. Here’s a rundown of the different types of optical filters featuring a wide range of coatings available on substrates like glass, plastic, metal and ceramic.
Taxonomy of Optical Filters
Without the full understanding of its purpose, an optical filter simply appears as an inconspicuous piece of glass or plastic. The design and treatment determine how it will alter the light resulting in a range of industrial, scientific, and consumer applications.
Also called interference filters, bandpass filters allow only a specific wavelength band to pass through. Physicists Charles Fabry and Jean-Baptiste Alfred Perot discovered the application of bandpass filters in astronomy as noted in the Astrophysical Journal. The Fabry-Perot interferometer earned its name due to their discovery.
Modern interference filters have their central wavelength tuned to address specific requirements in spectroscopy, photometry, clinical chemistry, or laser separation among others. An examination of the use of bandpass filters for astronomical photometry can be found in an article on filter profiles and zero points from the Astronomical Society of the Pacific.
Long- and Short-pass Filters
Long-pass filters transmit longer wavelengths of light while blocking shorter wavelengths. Short-pass filters serve the opposite purpose — transmitting shorter wave bands and blocking longer wavelengths. Fluorescence spectroscopy use such filters in, for example, cell biology or DNA studies, separating excitation energy from the fluorescence band.
Laser Line Filters
Lasers often emit radiation that is not totally monochromatic, and users rarely want other wavelengths to interfere with their primary purpose. A laser line filter eliminates this unfavorable radiation and allows engineers, doctors, and scientists to perform surgical procedures, enable fiber-optic communications, sequence DNA, create eye-popping laser light shows for theatrical productions, and much more.
These optical components reduce the intensity of light evenly across wide wavelength bands. For photographers wishing to alter shutter speed and aperture and thus create unique, experimental images that aren’t overexposed, neutral-density filters are essential, even for exposure lengths of 10 minutes or more at high F-stops.
Elaborate theatrical light shows and retail displays require the gamut of precise
colors to produce stunning visual effects. Dichroic filters, essentially color
separation filters, provide the means to control and project specific colors brightly and efficiently.
Color Temperature Correction Filters
It is necessary to ensure precise color integrity in photographic, stage lighting, medical and industrial applications. Color temperature correction filters control light-wavelength transmission and reflection as needed for the accurate appearance of even the most esoteric color blends. These coatings tolerate temperatures up to 650º C (1,202º F), making them ideal for high-intensity lighting.
UV-blocking filters protect objects from the depredations of ultraviolet light, such as delicate, sensitive and expensive works of art in an art or history museum. Optivex™ UV blocking filters ensure reliable UV protection without distorting colors in the visible-light region or absorbing excess heat.
Custom Optical Filters and Coatings
Whether you seek non-standard optical filters or want a particular material coating blend to meet your technical specs, our optical experts bring decades of experience and deep expertise in optics to help you design filters that match your requirements. Contact us today to learn more about custom options or request a quote.
Dynasil Corporation of America (NASDAQ: DYSL) develops and manufactures optics and photonics products, optical detection and analysis technology and optical components for the homeland security, medical and industrial markets. Combining world-class expertise in research and materials science with extensive experience in manufacturing and product development, Dynasil is selling and continuing to develop products for dual-mode radiation detection solutions for security and commercial applications and sensors for non-destructive testing. Dynasil has an impressive and growing portfolio of issued and pending U.S. patents. The Company is based in Newton, Massachusetts, with additional operations in Massachusetts, New Jersey, New York and the United Kingdom. More information about the Company is available at www.dynasil.com.