One Lens to Rule them All

A technical review of LED development and optical advancements

One Lens to Rule Them All

In ten years, LED lighting has gone from a technological buzzword to the industry standard, with exponential improvements in optical control and energy efficiency. How have LEDs changed? What challenges do product developers face? And what’s next for the technology?

The move to LED from traditional light sources has been transformational, energy savings have skyrocketed, and never have purchasers had such a wide range of products to choose from. But it was not always so, with early LED lighting pushing semiconductor manufacturers for greater efficacy and lower prices.

How LED Chips have Developed Over Time

Early Dual In-Line packages consisted of a rudimentary cathode and anode frame with wedge wire bonds, producing very low lumen output and poor optical performance. Encapsulated LEDs (often referred to as mid power LEDs) improved on this, with higher power and good lumens per dollar. A plastic reflector surrounded a chip held in epoxy encapsulant, with phosphor applied to adjust colour temperatures. These mid power LEDs suffered from poor lumen maintenance at high power, in part due to the degradation of the plastic reflectors.

The majority of the street lighting market today uses High Power Ceramic Package LEDs, a high power solution with excellent thermal performance – due to contact with a conductive base material. Ceramic packages moved LEDs beyond internal reflectors, instead using lens materials as a form of primary optic.

Chip On Board LEDs (COBs) offered a step change in maximum power from a single package, with potential outputs over 100 Watts. By mounting an array of LEDs onto a large aluminium substrate higher total flux can be offered with excellent thermal performance. A single phosphor coat is applied to the entire surface, offering good colour uniformity with a low profile form factor. Continual development of COB technology offers higher LED efficiency, which INDO has built into our ever-improving CHROMA and new CHROMA-X optics.

Chip Scale Package LEDs (CSPs) offer another paradigm shift in the way LED lighting is developed and built; effectively being a “package free” LED. The chip is constructed from the LED itself, an electrical bonding pad and phosphor coating – without substrate, reflectors, epoxy domes, bond wires or lead frames.

Closer view of a CSP

This incredibly small form factor offers both design opportunities and challenges.  The removal of a lead frame eliminates sulphur degradation, while the removal of bond wires massively increases product reliability.  More like a point source, these chips make optical control and achieving better cut-off angles much easier.

The challenge of CSPs

The small size of a CSP makes positioning within a lens even more important; with the 5-sided nature of the devices requiring extra attention for proper optical control. Small offsets can dramatically alter the photometric properties of a CSP luminaire, with additional care required during the manufacturing process – and novel design techniques needed to ensure foolproof assembly and product versatility.

CSPs now come as small as 1mm sq

Major manufacturers have been promoting CSPs for around 2 years, with many of the big players in the semiconductor market showing their product offerings at the Frankfurt Light & Building show in 2016.  However, lens solutions have not yet caught up with the optical challenges of such a small LED. To take advantage of the latest developments, INDO embarked on our own project to develop a CSP optical solution in Q4 2016.

The final result of that development was the new NAVIGATOR optical solution, a versatile light engine with a suite of 17 different distributions, offering improved optical control versus previous LED types and spring-boarding INDO to its next project – Variable Optics.

Variable Optics – A photometrically controllable solution

More accurate optical control and reduced lens size allows for the innovative development of variable optic luminaires – where the photometric properties can be controlled and changed on the board dynamically ,it is possible to develop a luminaire that can adapt to changing road conditions.  This puts absolute control into the hands of customers and integrates with a smart cities outlook.

The images and video below show a conceptual demonstration of these dynamically changing optics in a controlled test environment.

Left: Wider, more diffuse distribution
Right: Narrower, intense distribution

Watch closely – you’ll see the distribution slowly and gradually change!

What benefits could these patented Variable Optics from INDO offer?
  • Easier procurement and stores control with reduced stock holding units required
  • Enables adaptive luminaires that can be remotely adjusted post-installation to respond to changing environmental or situational factors
  • Allows for more efficient schemes, adjusting each lighting point as required
  • Potential resident complaint/response solution

With the ability to alter the effective area on a whim, asset managers can change the dynamic of their installations with simple commands, responding to changing requirements and resident feedback.

INDO is pushing forward with our developments in Direct Drive technology, offering a selection of optics and LEDs across our products. The INDO team continues to grow and learn; with technical expertise being poured back in to future development projects.

The latest light engine solutions will also be available in our new motorway luminaire, the AIR3 >