Distortionaberration

Reliability. Lower THD can improve the reliability of the LED fixtures and other devices on the same electrical system. This can reduce maintenance costs and increase the overall lifespan of the equipment.

Power Quality. High THD can disrupt power quality for other equipment in the facility. As power quality of the facility decreases, the electrical system will have less stable voltage and current, which affects the overall performance of the electrical system and other devices.

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Interference. High THD can cause electromagnetic interference (EMI) and other disruptions in nearby electronic devices. Lower THD reduces the risk of interference and makes the LED fixtures more compatible with other equipment.

In optical microscopy, refractive index is an important variable in calculating numerical aperture, which is a measure of the light-gathering and resolving power of an objective. In most instances, the imaging medium for microscopy is air, but high-magnification objectives often employ oil or a similar liquid between the objective front lens and the specimen to improve resolution. The numerical aperture equation is given by:

Energy Efficiency. Some may think that as long as you’re switching out higher consumption lighting for an LED, you’ll be efficient. Well, distorted current can lead to higher energy consumption and negate some of the energy-saving benefits of LEDs. It’s important to have LED fixtures with lower THD so the electrical current is closer to a pure sinusoidal wave, which improves energy efficiency.

Opticaldistortionmeaning

As the refractive index of a material increases, the greater the extent to which a light beam is deflected (or refracted) upon entering or leaving the material. The refractive index of a medium is dependent (to some extent) upon the frequency of light passing through, with the highest frequencies having the highest values of n. For example, in ordinary glass the refractive index for violet light is about one percent greater than that for red light. A consequence of this phenomenon is that each wavelength experiences a slightly different degree of refraction when a heterogeneous light beam containing more than one frequency enters or leaves the medium. This effect is termed dispersion and is responsible for chromatic aberration in microscope objectives.

where n is the refractive index of the imaging medium and θ is the angular aperture of the objective. It is obvious from the equation that increasing the refractive index by replacing the imaging medium from air (refractive index = 1.000) with a low-dispersion oil (refractive index = 1.515) dramatically increases the numerical aperture.

Heat Generation. Higher harmonic distortion means the system is working harder to produce what it is expected to produce. This increases heat generation in the electrical wiring and components, increasing the risk of overheating and shortening the lifespan of the fixture and other connected devices.

Where n represents the refractive indices of material 1 and material 2 and θ are the angles of light traveling through these materials with respect to the normal. There are several important points that can be drawn from this equation. When n(1) is greater than n(2), the angle of refraction is always larger than the angle of incidence. Alternatively when n(2) is greater than n(1) the angle of refraction is always smaller than the angle of incidence. When the two refractive indices are equal (n(1) = n(2)), then the light is passed through without refraction.

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Imagine a perfect electrical current waveform as a smooth sine wave. Electrical devices often introduce “harmonics,” additional current components at multiples of the main frequency (usually 60 Hz in the US). These harmonics distort the original sine wave, creating total harmonic distortion. Total harmonic distortion is expressed as a percentage. In this post, we’ll explain why lower percentages are beneficial when considering an LED conversion in your facility.

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World-class Nikon objectives, including renowned CFI60 infinity optics, deliver brilliant images of breathtaking sharpness and clarity, from ultra-low to the highest magnifications.

Refractive Index (Index of Refraction) is a value calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density. The refractive index variable is most commonly symbolized by the letter n or n' in descriptive text and mathematical equations.

LensdistortionExamples

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As presented in the figure above, a wavefront incident upon a plane surface separating two media is refracted upon entering the second medium if the incident wave is oblique to the surface. The incident angle (θ(1)) is related to the refraction angle (θ(2)) by the simple relationship known as Snell's law:

The switch to LED lighting offers tremendous benefits – energy savings, longer lifespans, and improved light quality. However, there’s one technical aspect to consider: Total Harmonic Distortion (THD).

Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.

Snell's law was originally defined by the relationship between the incident angles and the ratio of the velocities of light in the two media. The refractive index or index of refraction is the ratio between the velocity of light (c) in free space (for all practical purposes, either air or a vacuum) and its velocity η in a particular medium:

It’s important to consider THD in your LED upgrade, especially in manufacturing plants where processes can be easily affected by power quality and harmonics. Many manufacturers only advertise the life of their LED chips but do not consider the system as a whole. By understanding THD and making informed choices, you can ensure your LED lighting upgrade delivers optimal benefits without compromising the performance and efficiency of your entire electrical system.

LEDs themselves don’t generate significant THD. However, the power supplies (drivers) that convert AC power to DC power for the LEDs can. Low-quality drivers might introduce higher THD. So, it’s important to understand the LED system in its entirety.