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LED illumination | LED illumination

Key Words: diascopic, episcopic, illumination, metrology, edge detection, vision/video measuring

Definition:A light emitting diode (LED) is a semiconductor device that emits light when a voltage is applied to its terminals (electroluminescence)


Unlike a conventional filament bulb LED light sources are a 'cold' light source (do not generate any heat) that provide high intensity light similar to that of a halogen bulb. LEDs require very little maintenance and have a long life. They are also more efficient than tungsten bulbs in the amount of electrical energy that they are able to convert into light. There are many different types of LED, which generate light of different colors depending on the semiconductor material used (Gallium phosphide doped with oxygen produces red light, for example, and green light when doped with nitrogen, while gallium arsenide generates light in the infrared region). White LED light is particularly useful as an illumination source in microscopy and is produced by adding phosphors to blue LEDs. LED illumination can be attached to a microscope in a ring conformation to allow multidirectional lighting.


LED light can provide high intensity bright white light to produce excellent microscope illumination for a variety of imaging tasks. It has the advantage that is cold light and, therefore, cannot damage temperature-sensitive samples or cause temperature induced changes in focus, which could have an impact on accuracy in microscopic metrology applications. The ability to select directional light from a LED ring illuminator provides opportunities to create shadows or edges for measurement and inspection applications. The system makes possible observations of extremely low-contrast edges which are usually invisible under episcopic illumination. This is especially useful in enhancing edges of the contours of bosses, pins, ceramic packages, molds, medical devices and other three dimensional parts. Key words: metrology, vision/video measuring, illumination, edge detection, diascopic, episcopic


Nikon's Vision measuring systems incorporate episcopic, diascopic and an 8-segment ring LED illumination. The 8-sector LED ring illumination system consists of inner and outer ring illuminator, which has been especially developed for Nikon systems. The high-intensity white LED features constant color temperature and less flicker, thus it provides stable measurement accuracy, particularly when observing color images. With the LED's quick response to lighting controls, increased measurement throughputs can be achieved.

The MM400 and MM800 series of measuring microscopes include a white LED illuminator as standard for brightfield use. An 8-segment LED ring illumination, in addition, enables illumination control from eight directions, eliminating the need to pull out and adjust the fiber illuminator each time a measurement is made.


Please consult your local Nikon representative for advice suited to your imaging needs

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