Lyot depolarizer

In fluorescent tubes used for lighting, "ultraviolet radiation with a wavelength of 254 nm is produced along with the blue light that is emitted when an electric current is passed through mercury vapor," according to the University of Nebraska. "This ultraviolet radiation is invisible but contains more energy than the visible light emitted. The energy from the ultraviolet light is absorbed by the fluorescent coating inside the fluorescent lamp and re-emitted as visible light." Similar tubes without the same fluorescent coating emit UV light that can be used to disinfect surfaces, since the ionizing effects of UV radiation can kill most bacteria.

Sometimes the cells with DNA mutated by the sun's rays turn into problem cells that don't die but keep proliferating as cancers. "The UV light causes random damages in the DNA and DNA repair process such that cells acquire the ability to avoid dying," said Chuang.

UV radiation has enough energy to break chemical bonds. Due to their higher energies, UV photons can cause ionization, a process in which electrons break away from atoms. The resulting vacancy affects the chemical properties of the atoms and causes them to form or break chemical bonds that they otherwise would not. This can be useful for chemical processing, or it can be damaging to materials and living tissues. This damage can be beneficial, for instance, in disinfecting surfaces, but it can also be harmful, particularly to skin and eyes, which are most adversely affected by higher-energy UVB and UVC radiation.

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The result is skin cancer, the most common form of cancer in the United States. People who get sunburned repeatedly are at much higher risk. The risk for the deadliest form of skin cancer, called melanoma, doubles for someone who has received five or more sunburns, according to the Skin Cancer Foundation.

Many substances — including minerals, plants, fungi and microbes, as well as organic and inorganic chemicals — can absorb UV radiation. Absorption causes electrons in the material to jump to a higher energy level. These electrons can then return to a lower energy level in a series of smaller steps, emitting a portion of their absorbed energy as visible light. Materials used as pigments in paint or dye that exhibit such fluorescence appear brighter under sunlight because they absorb invisible UV light and re-emit it at visible wavelengths. For this reason they are commonly used for signs, safety vests and other applications in which high visibility is important.

The wedge depolarizer is the alternative form which should be used for monochromatic light sources. Again, a thick plate is manufactured in which the optical axis is in the plane of the plate. In use, the optical axis is aligned at 45° to the axis of the incoming polarized light and the thickness of the plate is varied in the plane of the incoming light (a wedge), thus producing a variable birefringence across the aperture of the plate. A second plate of index matching but non-birefringent material is added to the first plate to provide a compensation of the wedge angle, thus minimizing deviation of the beam but maintaining the depolarization. The most common combination is to use crystal quartz and fused silica, usually optically contacted together to enable applications into the ultra-violet.

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Another commonly used polarizer type is the Glan-Thompson. Although of much lower handling, it is characterized by a very large field of view which makes it ideally suited to imaging applications.

We offer calcite Glan-Taylors from 10mm upwards and in configurations with ground side faces or one or two polished side exits.

While exposure to UV light can lead to skin cancer, some skin conditions can be treated using UV light, according to Cancer Research UK. In a procedure called psoralen ultraviolet light treatment (PUVA), patients take a drug or apply a lotion to make their skin sensitive to light. Then a UV light is shone on the skin. PUVA is used to treat lymphoma, eczema, psoriasis and vitiligo.

Ultraviolet (UV) light falls in the range of the EM spectrum between visible light and X-rays. It has frequencies of about 8 × 1014 to 3 × 1016 cycles per second, or hertz (Hz), and wavelengths of about 380 nanometers (1.5 × 10−5 inches) to about 10 nm (4 × 10−7 inches). According to the U.S. Navy's "Ultraviolet Radiation Guide," UV is generally divided into three sub-bands:

The Lyot depolarizer is assembled from two or more plates of birefringent material, in each plate the optic axis of the crystal lies in the plane of the plate and is orientated at 45° to the axis of the previous plate. The plates are manufactured in a geometric sequence of thicknesses, each plate being twice the thickness of the next thinnest plate. In the simplest case of two plates, one is just twice the thickness of the other. A three-plate Lyot depolarizer requires one plate of thickness "t", one of thickness "2.t" and one of thickness "4.t". Depolarization is obtained through the production of varying amounts of circular and elliptical polarization states at different wavelengths. The depolarization effect is poor for monochromatic light as even with a large number of plates in the stack there are only a limited number of polarization states produced. By contrast, a polychromatic source will produce an effectively infinite number of polarization states and thus depolarization is strong, even with just two plates.

Lyot depolarizers can be manufactured in just about any birefringent material, but most applications are covered by either quartz or calcite. Quartz is particularly suitable for applications extending into the ultra-violet and we can provide optically contacted components for minimum insertion loss. For applications where calcite is more suitable, we can provide either cemented or even air spaced components (but calcite is not suitable for optical contacting).

Depolarizer in dry cell

Ultraviolet light is a type of electromagnetic radiation that makes black-light posters glow, and is responsible for summer tans — and sunburns. However, too much exposure to UV radiation is damaging to living tissue.

It may seem counterintuitive to treat skin cancer with the same thing that caused it, but PUVA can be useful due to UV light’s effect on the production of skin cells. It slows down the growth that plays a major role in the disease’s development.

Although this page is about devices to randomize polarization, we of course also make other optical elements to polarize light and then to control its polarization state.

Leysop can provide these components in whatever diameter, thickness, number of sections you require (we have manufactured 22 section Lyot depolarizers for one especially critical application) and with or without AR coatings, as you prefer. Components can be provided mounted in protective rings or supplied bare. Please enquire with us for your specific requirements and provided it is possible we would be happy to meet your needs.

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A suntan is a reaction to exposure to harmful UVB rays. Essentially, a suntan results from the body's natural defense mechanism kicking in. This consists of a pigment called melanin, which is produced by cells in the skin called melanocytes. Melanin absorbs UV light and dissipates it as heat. When the body senses sun damage, it sends melanin into surrounding cells and tries to protect them from sustaining more damage. The pigment causes the skin to darken.

Depolarizer in Leclanche cell

According to Robert Patterson, a professor of astronomy at Missouri State University, most observations are conducted using charge-coupled devices (CCD), detectors designed to be sensitive to short-wavelength photons. These observations can determine the surface temperatures of the hottest stars and reveal the presence of intervening gas clouds between the Earth and quasars.

"Melanin is a natural sunscreen," Gary Chuang, an assistant professor of dermatology at Tufts University School of Medicine, told Live Science in a 2013 interview. However, continued exposure to UV radiation can overwhelm the body's defenses. When this happens, a toxic reaction occurs, resulting in sunburn. UV rays can damage the DNA in the body's cells. The body senses this destruction and floods the area with blood to help with the healing process. Painful inflammation occurs as well. Usually within half a day of overindulging in the sun, the characteristic red-lobster look of a sunburn begins to make itself known, and felt.

Just as important for many applications as having a well polarized source, it is sometimes necessary to ensure that a source is completely free of any preferred plane of polarization. An example of this is a sensitive spectrometer where varying degrees of polarization will lead to measurement errors. Of course, in nature almost all sources exhibit some degree of polarization, even thermal sources become polarized after reflection from a dielectric surface. Depolarizers are therefore essential items to have wherever a completely un-polarized source must be used. There are two principle methods of producing a depolarization but they operate in different manners and it is essential that the correct type is chosen based on whether the source is mono- or poly-chromatic.

The guide goes on to state, "Radiations with wavelengths from 10 nm to 180 nm are sometimes referred to as vacuum or extreme UV." These wavelengths are blocked by air, and they only propagate in a vacuum.

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Black-light tubes typically use mercury vapor to produce long-wave UVA light, which causes certain dyes and pigments to fluoresce. The glass tube is coated with a dark-purple filter material to block most of the visible light, making the fluorescent glow appear more pronounced. This filtering is not needed for applications such as disinfecting.

Fluorescence can also be used to locate and identify certain minerals and organic materials. According to Thermo Fisher Scientific, Life Technologies, "Fluorescent probes enable researchers to detect particular components of complex biomolecular assemblies, such as live cells, with exquisite sensitivity and selectivity."

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Besides the sun, there are numerous celestial sources of UV radiation. Very large young stars shine most of their light in ultraviolet wavelengths, according to NASA. Because Earth's atmosphere blocks much of this UV radiation, particularly at shorter wavelengths, observations are conducted using high-altitude balloons and orbiting telescopes equipped with specialized imaging sensors and filters for observing in the UV region of the EM spectrum.

The same skills which we employ to fabricate our own designs of optical components may be applied to your own designs, whether they be in crystal or glassy materials. As long as it has flat surfaces, we can probably make it.

Most of the natural UV light people encounter comes from the sun. However, only about 10 percent of sunlight is UV, and only about one-third of this penetrates the atmosphere to reach the ground, according to the National Toxicology Program (NTP). Of the solar UV energy that reaches the equator, 95 percent is UVA and 5 percent is UVB. No measurable UVC from solar radiation reaches the Earth's surface, because ozone, molecular oxygen and water vapor in the upper atmosphere completely absorb the shortest UV wavelengths. Still, "broad-spectrum ultraviolet radiation [UVA and UVB] is the strongest and most damaging to living things," according to the NTP's "13th Report on Carcinogens."

Recent research suggests that UV light may have played a key role in the origin of life on Earth, especially the origin of RNA. In a 2017 article in the Astrophysics Journal, the authors of the study note that red dwarf stars may not emit enough UV light to start the biological processes needed for the formation of ribonucleic acid, which is necessary for all forms of life on Earth. The study also suggests this finding could help in the search for life elsewhere in the universe.

A number of artificial sources have been devised for producing UV radiation. According to the Health Physics Society, "Artificial sources include tanning booths, black lights, curing lamps, germicidal lamps, mercury vapor lamps, halogen lights, high-intensity discharge lamps, fluorescent and incandescent sources, and some types of lasers."

Electromagnetic radiation comes from the sun and transmitted in waves or particles at different wavelengths and frequencies. This broad range of wavelengths is known as the electromagnetic (EM) spectrum. The spectrum is generally divided into seven regions in order of decreasing wavelength and increasing energy and frequency. The common designations are radio waves,microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays and gamma-rays.

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One of the most common ways of producing UV light is passing an electric current through vaporized mercury or some other gas. This type of lamp is commonly used in tanning booths and for disinfecting surfaces. The lamps are also used in black lights that cause fluorescent paints and dyes to glow. Light-emitting diodes (LEDs), lasers and arc lamps are also available as UV sources with various wavelengths for industrial, medical and research applications.