Almost everything emits, reflects, or transmits some kind of light. The Electromagnetic (EM) Spectrum is the measurement of the frequency range of EM radiation of an object. The frequency is measured in wavelengths. The wavelength ranges can extend from the size of an atom to thousands of kilometers.
The long wavelengths are low frequency and are the Radio, Microwave, and Infrared waves. The short wavelengths are the high-frequency Ultraviolet, X-ray, and Gamma Rays. The Visible Spectrum, or Optical Spectrum, is the range of the Electromagnetic Spectrum that is visible by the human eye.
Electromagnetic Spectrum
The Visible Spectrum has no clear boundaries from one color to the next but is generally described in the following ranges:
Color | Frequency | Wavelength |
Violet | 668–789 THz | 380–450 nm |
Blue | 606–668 THz | 450–495 nm |
Green | 526–606 THz | 495–570 nm |
Yellow | 508–526 THz | 570–590 nm |
Orange | 484–508 THz | 590–620 nm |
Red | 400–484 THz | 620–750 nm |
*Nanometer - a unit of length in the metric system, equal to one billionth of a meter, which is the current SI base unit of length. It can be written in scientific notations as 1×10-9 m (engineering notation) or 1 E-9 m (exponential notation), both meaning 1/1,000,000,000 meters
History
Newton divided the spectrum into seven named colors: red, orange, yellow, green, blue, indigo, and violet, or ROY G. BIV. Originally only five primary colors were named: red, yellow, green, blue, and violet, but later he added indigo and orange to have seven colors. The need for the number seven was derived from the belief that it should match the number of known planets, the number of days in a week, and the number of notes on a major scale. This theory was derived from ancient Greek Sophist philosophy.
The word Spectrum is Latin for apparition and was coined by Newton during his experiments with light. He observed that sunlight passing through a prism produced the apparition or spectrum or, in other words, a band of colors.
Sir Isaac Newton wrote Optick's released in 1704, hailed as one of the earliest explanations of the Spectrum.
Optics
The field of optics usually describes the behavior of visible, infrared, and ultraviolet light; however because the light is an electromagnetic wave, analogous phenomena occur in X-rays, microwaves, radio waves, and other forms of electromagnetic radiation. Optics can thus be regarded as a sub-field of electromagnetism.
Camera Vision
In vision applications that use camera technology the optical fields of visible, infrared, and ultraviolet are the most widely used, and with the implementation of specialized optics, filters, and lighting many solutions to imaging issues can be found. Infrared Radiation (IR) is a wavelength longer than visible light but shorter than radio waves (750nm to 1nm). Ultraviolet (UV) is shorter than visible light but longer than X-Ray (400nm to 200nm Near UV, NUV). Most cameras will fall in the near IR or near UV range and with the use of specialized lighting (LED’s), enhancement of the wavelengths is possible.
Infrared (IR) camera technology is very common in military applications and Ultraviolet (UV) solutions are used in various machine vision, and industrial imaging applications. Forward Looking Infrared or FLIR cameras are very popular in military and commercial applications. FLiR Cameras Boson 320, Boson 640, and the FLiR Tau2 are widely used by companies integrating infrared camera technology (IR cameras) into their systems. For more information on IR Cameras call David Naranjo, 760-729-2026.