There are some very elegant lighting solutions -flat panel light fixtures for the surface mounting retrofit application beyond the traditional wraps/pendants lights options.
 |
| Traditional surface mount Wraps(1*4) |
These new flat panels style fixtures deliver a slim thinner profile, even light distribution with less glare, and better aesthetic look when compare with other traditional surface mounting fixtures.
For these type of flat panels, they come in different sizes from 2*2 ft, 2*4 ft, 1*4 ft and with a overall thickness from 1 inch to 4 inches.
It could be categorized into two different type lighting technologies:
Edge Lighting( Edge-Lit) and
Back lighting( Back-Lit). Both of these technologies has been successfully used in consumer electronics displays ( such as mobile devices and TVs ).
Edge Lighting has light up LEDs sitting around the edges of the wave guide panels. The emitted lights from leds couple into the waveguide optics, then will be guided by Total Internal Reflection and redirected evenly to the front of the Light guide optics by the molded/etched pixel-based micro-optical light-extraction features. It also needs highly reflective Back Reflector that help recycle the light extracted from the leds and redirect the light emit to the room side. The diffusion films and other optic films on top of the Light Guide Panel( LGP) is used to reduce glare and achieve the right light distribution type.
Edge lightings use the highly efficacious LEDs on the edges surrounded the LGP, but the led radiation angle (viewing angle/directivity) is typically from 90 to 120 degrees, that means some lights can not fully couple to the LGP , but may be trapped around the Edges and housings. Sometimes designer can add side reflectors around the edges to recycle the lights.
It typically requires the LEDs lighting emitted surface to be very close proximity to the LGP (0.3mm to 0.5mm), and also have mechanical stoppers along the LED light engines to limit the interferences between LEDs and LGP due to thermal expansions and machining tolerances of LGP edges.
The SMD leds’ light emitting area can vary from 2.6mm*2.6mm to 2.5mm*1.15mm size.
The smaller leds tend to have lower efficacy, but the fixture can use a thinner thickness LGP to save costs/weight. The light engines will need have good thermal dissipation to get rid of the heat quickly to avoid LED thermal droop of overheat. The housing frames where the light engine mounted typically made of metal frame for the higher lumens package fixtures.
The wave guide materials can be “lighting grade” acrylics(PMMA) which have lower transmittivity properties. The LGP material also need to withstand heat, UV, yellowing and long-term optical performance degradations. To micro-lens type light guided design, laser etching, chemical etching and shape painting are used to create the diffuse light extraction features.
The light extract from single side could progress to the center of LGP with a reduced intensity, and it is common to implement leds light source on the opposite edges to maintain the overall light uniformity of the whole illuminated area. To achieve higher lumens package and higher fixture efficacy, the manufacture can always consider 1 side ,2 sides or 4 sides light up strategy. The complexity of manufacturing will increase when there are more light up edges with the stringent controls on assemble tolerances. The fixture’s cost will go up as well due to that.
The biggest benefits of Edge lit fixture is the thinner overall height, uniformity in light distribution and less glare or pixilation, but the competition of efficacy and energy saving purpose, the edge lite product tends to less ideal. Most of the Edge lighting fixture can meet Energy star and DLC standard, it would be hard to meet the DLC premium standard without adding more leds and significant under driving leds.
The Back Lighting panel tends to solve this efficacy concern more economically by avoiding the complex and costly LGP optics system by utilizing small/micro optics directed placed on top of leds to spreading lights evenly across the whole light-up area and reduce hotspots and optical gap in the light mixing chamber. It also uses the diffuser plate and films to remove any glare and pixilation. The back lite panels is still in a thin profile and without the dramatic light pixilation and a uniform light distribution just like the edge light fixtures. The fixture efficacy can be much higher than the edge light panel using the same leds count and driver wattage. The overall fixture height could be sacrificed a bit by increase from 1 inch of edge lit to above 2 inches of back lit. The fixture can even deliver even higher lumens packages with a better control on light engine thermals with the bigger optical gap and volume in optical chamber.
The bubble optics is adopted form the similar technology used in a lot LED/LCD TV backlights. The optics can help spreading the light distribution to be a bat-wing shape to achieve better uniformity in a short distance of optical gap. The optics will need some type of epoxy or glue to be able fully secured on to the light engine and on top of leds. The optics’ optical efficiency needs to be above 90% and heat resistant optical quality material. The extra cost of bubble optics is offset by the elimination of LGP optics.
 |
| bubble optics |
 |
| Light distribution of bubble optics |
These panels can be surface mounted or suspended mounted as they are typically light weight due to the very thin profiles.
More and more of these panels become very popular in the retrofit application due to its easiness to be installed and even field configurable Light outputs and CCT features.
Check out how easy it is edge lite fixture panel installation video.
