LED optical systems
The quality of the optical systems greatly affects the overall efficiency of an LED luminaire. To produce directed light, as occurs in spotlights, ERCO develops their optical projection systems in-house. A collimating lens, as a secondary lens, is the interface between the LED lens on the printed circuit board and the exchangeable Spherolit lenses acting as tertiary lenses. The collimating lens directs the light of the LEDs into a parallel beam in order that the required light distribution can then be created by the tertiary lens. The principle of total internal reflection in the collimating lens contributes to the high efficiency of the optical system. Decades of experience in injection-moulded polymers ensure the highest quality levels from our in-house production plant.
Optical principle The light is guided by three elements in an ERCO LED spotlight: the primary lens which is directly mounted on the LED chip and produces a semi-spherical beam, the secondary lens in the form of a collimating lens to create a parallel beam and the tertiary lens in the form of a Spherolit lens. The design of the tertiary lens determines the actual light intensity distribution for the specific application.
Collimating lens For all light intensity distributions - except for narrow spot - the threepiece collimating lens is suitable for the module with three LEDs. The beam is controlled by total internal reflection at the sides and by the central lens. Precise mounting points result in secure and effective mounting.
Collimating lens for narrow spot The appropriate collimating lens is used with LED spotlights and projectors with the narrow spot characteristic. Its function is solely based on the optical principle of total internal reflection, which contributes to the high efficiency of the optical system.
Total internal reflection
Spherolit lens
Due to its shape and material, the collimating lens for narrow spot directs the light with practically no losses using the principle of total internal reflection. This results in optimum light guidance efficiency.
After focusing the beam through the collimating lens, it is the Spherolit tertiary lens that determines the light distribution. This ranges from narrow beams to wide beams and asymmetrical light intensity distributions for vertical illuminance.
Development
With extensive experience in optical simulations, ERCO identifies innovative solutions for new challenges such as the development of highly efficient lens systems.
Short distances for optimum quality: photometric laboratories, tool shop and production department for the optical systems are all located on the same site. This allows for rapid comparison of computer simulations, prototypes and fabricated components.
Projection and reflection
Conventional point light sources emit light in a solid angle of virtually 360°, whereas the inherent design of LEDs means their light is directed in a solid angle of <180°. The result is reduced losses due to spill light or light emitted towards the lampholder (shown red in the drawing). Furthermore, the higher transmission efficiency of lenses compared to that of reflectors produces a higher light output ratio which results in the greater luminous flux from the luminaire. In practice it comes down to how much light arrives on the target surface. In this respect, the illuminance from spotlights which have similar characteristics can be compared over a given distance in lx/W: the principle of projection with LEDs continues to be convincing.
Projection: Spherolit lenses
With LED lighting tools for directed light, ERCO uses Spherolit lenses as tertiary lenses to direct the light. In terms of their technology and light distribution, the Spherolit lenses are based on the patented Spherolit reflectors which are well established with conventional light sources. In addition to excellent lighting quality, they also offer many practical advantages for both lighting designers and users. The Spherolit technology is based on dividing a large lens or reflector surface into many individual, three-dimensionally domed facets, each of which directs the light through refraction or reflection. The transmission of light through the polymer Spherolit lens has fundamentally lower losses than with reflection. At ERCO, the manufacturing processes all take place under one roof: from complex calculations and computer simulations to tooling up and final production.
Characteristics with Spherolit lenses
Narrow spot To accentuate small objects with high light intensity or to cover large distances between luminaire and object. Beam angle < 10°.
Spot
The light intensity distribution for highlighting objects of all types, especially to accentuate three-dimensional shapes.
Beam angle: 10° - 20°.
Flood
To efficiently illuminate larger objects or to emphasise spatial zones such as a specific area.
Beam angle
25° - 35°.
Wide flood To give a flexible, flood illumination of surfaces and spatial zones, especially in retail presentation. Beam angle> 45°.
Oval flood The Spherolit lens, oval flood, has an axially symmetrical light intensity distribution, producing an oval beam of about 30° by 90°.
Wallwash The light intensity distribution of the lens wallwasher is designed to provide very good uniformity.
Spherolit lens toolmaking
Toolmaking ERCO has its own toolmakers´ shop featuring state-of-the-art equipment and backed up by decades of experience. This guarantees the necessary precision when machining items such as injection-moulding tools used to make optical elements from polymers.
Thermoplastic injection moulding Cutting-edge injection-moulding machines, qualified employees, high-quality raw materials and careful checking all contribute to the perfect quality of ERCO´s collimating and Spherolit lenses.
Assembly The luminaires of the Quintessence product range, such as the directional luminaire shown here, are assembled to order using advanced production principles.
Spherolit lenses
By designing the shape of each Spherolit lens individually, a wide range of lens characteristics can be created. The parallel incident light is spread to a greater or lesser extent depending on the curvature of the surface. This results in lenses that have different beam angles, ranging from narrow spot to wide flood, yet retain the same overall geometry. In addition, asymmetrical spherolites enable oval beams and wallwashing lenses. A common feature of all these beam characteristics is light of the highest quality: the beams are particularly uniform, free of striations and have a clean, slightly soft edge.
SpotThe Spherolit lens, spot, has flat Spherolit surfaces producing low dispersion for a narrow beam angle.
Wide floodThe wide flood Spherolit lens has the greatest curvature. The wide spread produces a beam with a large emission angle.
Spherolit lens for varychrome RGBW spotlights An additional layer in the optical system is used to ensure full mixing of coloured light even before collimator and Spherolit lens shape it into the required beam. The result: LED light in any hue, of any colour temperature, completely free of irritating colour shadows.
Reflection
Especially in LEDs where high visual comfort is required ERCO uses optical systems based on the principle of reflection. This is the case in the Quintessence range of recessed luminaires with darklight reflectors. Here, to provide optimum glare control, the illuminated plane of the diffuser is set back from the plane of the mounting surface. This allows the exact cut-off angle to be defined. Darklight reflectors with Spherolit wallwasher segments produce asymmetrical light intensity distributions for energy efficient washlights and double washlights. To meet the stringent quality requirements, ERCO carries out all calculation, design and production work in-house.
Light mixer The upper reflector of Quintessence LED downlights is divided into eight segments and is made of mirror-finish aluminium. The reflections within this light mixer ensure the best possible colour mixing from immediately in front of the luminaire especially with RGBW LED modules.
Diffuser The purpose of the diffuser technology is to optimise the visual comfort. The frosted glass diffuser reduces the high luminance of the individual LEDs and disperses this evenly across its surface to reduce the glare. The diffuser technology enables the design and construction of high-quality, energy-efficient washlights.
Spherolit wallwasher To achieve the uniform vertical illuminances required for wallwashing, one segment of the Darklight reflector is provided with spherolites. In the photo, the diffuser has been removed to show the position of the LED module. The patented reflector technology results in the light on the wall beginning just below the ceiling.
Indirect step lighting
With step lighting, it is imperative that the LEDs are well screened to ensure that there is no glare for people going up the stairs. In the Axis Walklight, the light guidance takes place indirectly. The LED module is concealed from view.
Manufacture of Spherolit reflector
The patented Spherolit reflectors are of pressed aluminium. Their innovative technology requires the highest precision and calls for a new approach both in toolmaking and in the manufacturing process.
The finished Quintessence luminaire
is built to order from a combination of LED module and a lower reflector unit. Here, innovative technology such as "Pick by Light" shelves ensure error-free order completion.
Cut-off angle and Darklight technology
A cut-off angle of 30° (left) provides good uniformity on the floor with a very high lighting output ratio.
Luminaires with a cut-off angle of 40° (right) provide higher visual comfort. This can also be seen from the UGR values in the product data sheets. If the observer is in the cut-off area of the luminaire, the reflector will appear glare free.
With their computer-generated contours, ERCO's Darklight reflectors combine maximum visual comfort with high light output ratio. As long as the lamp is within the cut-off area, there is virtually no luminance on the Darklight reflector - the eye is not dazzled. For optimum visual comfort, the higher cut-off angle is recommended for prestigious rooms with high ceilings or for deskwork. The UGR process (Unified Glare Rating) quantitatively evaluates psychological glare. A downlight with a cut-off angle of 40° and a UGR value of 17.3 provides more visual comfort than an otherwise identical luminaire with a 30° cut-off angle and a UGR of 19.0.
By using dedicated PCB layouts equipped with carefully selected LED binnings, ERCO ensures that optimum luminous flux and colour rendition is obtained for each specific lighting task.
The optical systems for LED lighting tools are vastly different from those of conventional luminaires. ERCO designs and builds these systems in-house to ensure a perfect match, thereby allowing their full potential to be exploited in terms of efficiency and lighting quality.
ERCO places particular importance on heat management. This ensures that LED modules operate within their safe temperature range, achieving rated life and output for the specified power throughout their operational life.
LEDs require perfectly matching electronic control gear. The development of electronic modules in-house gives ERCO freedom in designing the form and function of innovative lighting tools.
LEDs and digital lighting controls such as Light System DALI are truly made for each other. No other light source can be controlled as flexibly and efficiently as an LED. The user-friendly operation through lighting control allows great scope to design scenographic lighting in the sense of "tune the light", this enables the potential energy saving to be fully realised.
