What is an LED magnifier light
An LED magnifier light is an integrated assembly of an LED light and a convex lens of positive power which combine to illuminate and enlarge small details so a task can be performed with more precision. The illuminated magnifier provides task illuminance uniformly over the field of observation, making an in-focus and highly defined view of surface details available in any visual environment.
Applications
The ability to deliver visibility beyond normal vision lends LED magnifier lights to a variety of applications. Aged and low vision population rely on the use of illuminated magnifiers to create a supportive visual environment. Hobbyists, needleworkers, clockmakers, cosmetologists, crafters, and artists use these products to support their hands-on work. In the electronics industry illuminated magnifiers are an indispensable tool for PCB inspection, assembly and rework. The same importance also applies in other industries that manufacture and engineer extremely tight tolerance, build-to-specification precision products. A variety of health care practices count on illumination and magnification provided by LED magnifier lights. These luminous magnifying devices provide crucial visibility for dermatological, dental and vascular surgeries, and other procedures involving detail-intensive diagnosis, prognosis, prevention, treatment, or palliation.
Design and construction
Integrated LED magnifier lights have a universal configuration. The LEDs that are assembled in modules are mounted around or on the side of the convex lens. The lens assembly is mounted on a gooseneck or articulating arm which allows the illuminated magnifier to adjust flexibly in position and angle. Illuminated magnifiers may be of the freestanding type with stability provided by a weighted base or may be equipped with clamp-on, screw or magnetic mounts. For applications where electrostatic discharge from the fixture is a concern, an anti-ESD coating that alters the electrical characteristics at the lens surface should be applied to the lens. The housing, arm and base may be powder-coated with a metal-laced conductive paint so as to effectively distribute the charge throughout the entire surface of the light fixture.
Magnifying lens
Obviously, a principal product differentiator of illuminated magnifiers is the magnifying lens which is made of either crystal clear acrylics (PMMA) or optical grade glass. Magnifying lenses are available in different sizes, diopters, focal lengths, and percentages of magnification. Diopter indicates the optical power or the refractive (light bending) capacity of a convex lens. Each diopter increases the size of the viewed object (magnification) by 1/4 (25%) when the object is at its full focal length (distance from the lens center to the viewed object when in focus) from the lens. As magnification increases, the viewing area and focal length decreases. The lens refractive capacity of hands-free magnifier lights typically comes in the range of 3 to 5 diopters. For additional magnification a secondary lens normally of a higher optical power may be movably attached to the primary lens.
LED module
An LED magnifier light may use one or more LED modules to distribute light uniformly around the magnifying lens. The LED module is comprised of an array of discrete SMD LEDs which are solder mounted a metal core printed circuit board (MCPCB). It is attached to aluminum heat sink which dissipates thermal energy generated at the LED junction to the ambient air. The high flux density light from the LEDs is regulated by either an opal diffuser or a gaussian/prismatic diffusing lens. The correlated color temperature (CCT) generally falls in the neutral white range (in the neighborhood of 4000K) however warm white and cool white light also finds their use. For general task lighting, a minimum color rendering index (CRI) of 80 will suffice. Nonetheless many professional and industrial applications require the light source to reproduce the colors of various objects as faithfully as possible. This calls for the use of spectrally optimized LEDs which deliver radiant power fairly uniformly across the visible spectrum and have a CRI exceeding 90.
Driver circuit
The LEDs can be battery operated or AC powered. The power fed to the LED load must be regulated by a constant current LED driver. LED drivers that run off AC power should provide complete suppression of the alternating waveform so that the LEDs will be driven by precisely regulated DC power having very small ripples. Large ripples in the output current provided to the LED load can cause LEDs to flicker and thus compromise visual comfort. Electromagnetic interference (EMI) suppression must be taken into account in the driver design when the LED magnifier lights are used in environments with the presence of EMI-sensitive equipment.
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