EDI-T® :
Technological Surprises to Sharpen Cutting
Edges of
Flashlights have been around for a long time and come
in a considerable variety of styles and configurations, but most of them
are traditionally comprised of a battery, a switch, a light source, an
optically plane window, and/or a light reflector packaged in a portable
form. Unfortunately, optical lenses are not implemented by the traditional
flashlights owing to the poor beam characteristics of the incandescent
bulbs. By introducing point-light-sources of HB LEDs into our flashlights,
it makes feasible to implement optical lens systems and produce peerless
light beam performances. Lenses are precise optical components, which are
expensive and difficult to manufacture. Before a lens can be constructed
it must be properly designed, that is to say, the radii of curvature of the
surfaces, thickness, diameters, apertures, and types of materials must all
be determined and specified precisely. The reason for the complexity in lenses is
that in the ideal case all the light rays in all wavelengths originating
at a given object point should be made to pass accurately through the
image of that object point, and the image of a plane object should be a
plane, without any appearance of distortion in the images of straight
lines. Lenses falls into several well-defined and well-recognized types,
many of which are listed over here for your easy references:
1. Plano-Convex (PCX) lenses have a positive focal length,
making them ideal for collecting and focusing light in imaging
applications. They are also useful in a variety of applications involving
emitters, detectors, lasers and fiber optics. Coated versions have optimum
light transmission. There are a wide variety of diameters and focal
lengths commercially available.
2. Plano-Concave (PCV) lenses have one flat and one inward
curved surface. PCV lenses have a negative focal length and are used for
image reduction or to spread right.
3. Double-Convex (DCX) lenses have two outward, equally
curved surfaces, a positive focal length, and are useful for 1:1 image and
in multi-element systems.
4. Double-Concave (DCV) lenses
have two inward, equally curved surfaces and a negative focal length. They
are used for image reduction and to spread light.
5. Ball lenses are great tools for improving signal
coupling between fibers, emitters and detectors. When coupling light from
a laser into a fiber, the choice of the ball is dependent on the NA
(Numerical Aperture) of the fiber and the diameter of the laser beam. The
diameter of the laser beam is used to determine the NA of the ball lens.
The NA of the ball lens must be less than or equal to the NA of the fiber
in order to couple all of the light into the fiber. The fiber should be
placed at the focal point of the ball lens.
6. Half-Ball (hemispherical) lenses are ideal for
applications such as fiber communications, endoscopy, microscopy, optical
pick-up devices and laser measurement systems.
7. Drum lenses are glass or plastic spheres,
ground down axially to provide a mounting surface. The ground
circumference simplifies handling issues typically associated with ball
lenses. They are ideal for optical transmission in fiber communications.
8. Cone lenses can be used for 3600
illumination and image processing applications. They are designed in
coated and uncoated versions to allow special applications. Cone top and
base are normally polished. Circumference is ground.
9. Rod lenses are polished on the circumference
and ground on both ends. Collimated light passing through the diameter of
the rod will be focused into a line. 450 Rod lenses can be used
to bend image paths or redirect light at 900. Small diameter
makes them ideal for use in fiberscope and borescope applications, where
size is critical. Elliptical surface, ground circumference and base are
normally polished.
10. Aspheric lenses offer superior aberration
correction
and are used primarily in high efficiency illumination
systems, . They are usually mounted in pairs, so that their convex
surfaces are nearly in contact. These systems require lenses somewhat
larger in diameter than the diagonal measurement of the slide or target
projected.
11. Fresnel lenses replace the curved surfaces of conventional lenses with a series of concentric grooves, molded into the surface of a thin, light-weight plastic sheet. The grooves act as individual refracting surfaces, like tiny prisms when viewed in cross section, bending parallel rays in a very close approximation to a common focal length. Because Fresnel lens is thin, very little light is lost by absorption. Fresnel lenses are a compromise between efficiency and image quality. High groove density allows higher quality images, while low groove density yields better efficiency (as needed in light gathering applications). In infinite conjugate systems, the grooved side of the lens should face the longer conjugate, such as condenser systems or emitter/detector setups; Fresnel lenses can also be used as magnifiers or projection lenses; however, due to their high level of distortion, this is not recommended.
1. Plano-Convex (PCX) lenses
2. Plano-Concave (PCV) lenses
3. Double-Convex (DCX) lenses
4. Double-Concave (DCV) lenses
5. Ball lenses
6. Hall-Ball (hemispherical) lenses
7. Drum lenses
8. Cone lenses
9. Rod lenses
10. Aspheric lenses
11. Fresnel lenses
More information on Optic Lenses can be found at FAQs of EDI-T® Battery-Free & Consumption-Free LED Flashlights.