Solais

Understanding Optics and the Benefits of LED Optical Control

admin — Thu, 12 May 2011 15:49:14 +0000

The most common mistake in lighting terms associated with the quantity of light is between the intensity of a light source and its total output. The total output of a light source is described in “lumens”. Lumens have no implication of the direction or distribution of light, or the area to which the light is incident on. The intensity of a light source is described in “candelas” and is defined as the total luminous flux (total lumens) within a given solid angle.

To better understand light output versus intensity, think of your oven. If you preheat the oven to 350^o, it will still be at 350^o regardless of where you stand. However, if you stand right next to the oven you will feel the heat much more than you will if you stand 5 feet away. In this example, the oven temperature is just like light output, where a 1000 lumen lamp will always have 1000 lumens regardless of where you stand or where you aim it. The amount of heat you feel depending on where you stand is just like light intensity, where the candela value will get lower the further you are from the light source. For different types of light sources, such as directional lamps, the candela value will also get lower the greater the angle you are from the center point of the beam. This center point is known as the “center beam candle power”, or CBCP.

In discussing reflector style lamps, terms such as “beam angle”, “field angle” and “beam spread” are most commonly used to describe distribution patterns, but these terms are often mistakenly substituted for one another.

Beam spread is a general term that frequently causes more confusion than clarity. The Illuminating Engineering Society of North America (IESNA) defines beam spread as the angle between the two directions in a plane in which the intensity is equal to a stated percentage of the maximum beam intensity. This means that it can be the same value of either beam angle or field angle, depending on how it is specified. To avoid this unnecessary confusion and also obtain an accurate and complete description of a distribution pattern, beam angle and field angle should be used.

Beam angle is the angle between the two opposite points at which the maximum intensity (center beam candle power or CBCP) is at 50%. This is the distribution value that is most commonly known and used in the lighting industry. It is also the value that frequently comes with the notations, “spot” or “flood”. For example, a 10˚ spot is a lamp with where 50% intensity is at an angle of 5˚ on either side of its CBCP.

Field angle is the angle between the two opposite points at which the maximum intensity is at 10% (See diagram). This value is often overlooked when it comes to directional lighting, but it is important to include because it helps to describe the expected gradient of the light output. For example, if the field angle is very close to the beam angle, then there will be a very sharp cutoff of light output. This is what would be expected out of a spot light used in theater stage lighting (see diagram). If the field angle is much larger, say double that of the beam angle, then there will be a larger gradient and therefore a softer cutoff of light output. This is what should be expected from most lamps intended for general lighting purposes.

LED reflector style lamps are available with different beam angles, similar to incandescent sources. This includes the narrow coverage spot lights (such as a 10 degree beam angle), wide coverage flood lights (such as a 40 degree beam angle), and everything in between. In fact, optical control (both beam and field angles) with LED sources is often easier to accomplish than in incandescent sources which is why high quality LED reflector style lamps have very smooth even light distributions with limited spill and striations.

The benefit of quality LED optics is often discussed without many people realizing it. Many times, people will describe LED reflector style lamps as having more “punch” than halogen lamps with their equivalent lumen output. This is entirely due to the control of the optics. For example, in a 10 degree LED spot lamp with 1000 lumen light output, virtually all of the 1000 lumens can be delivered to the desired area if high quality lenses are used. If you take a 10 degree halogen spot lamp with 1000, where there can be more than a 10% light loss due to the inefficiency of metal reflectors, only 900 lumens may be delivered to the desired area.

Important Things You Should Know When Evaluating LED Lighting

admin — Fri, 15 Apr 2011 15:31:07 +0000

LED sources are a new solution for virtually all lighting needs and have the potential to change the way we live and consume energy. The largest limitation currently slowing the adoption of LED lighting is simply that it is new and not well understood. In addition, the LED lighting market is flooded with products of varying quality which cause many to discount the technology altogether.

This article explains the basics of LED Lighting and why it is a wonderful upgrade for most conventional technologies. As a result, you will have a better understanding of the technology and will be in a position to ask the right questions and successfully select the appropriate LED solution for your desired application.

Correlated Color Temperature (CCT)

Correlated color temperature, or CCT, is a metric developed to describe the shade of “white” light that a light source emits. LEDs are inherently monochromatic light sources and therefore typically use phosphors to create “white” light. The benefit to this is they are available in various CCTs and are ideal for a wide range of applications. For example, home environments typically feature warmer softer shades of light, such as the yellow/orange found in incandescent sources which have CCT values in the 2700K-2900K range. Opposite this, many institutional applications (surgery suites, science labs, etc) require a very crisp cool shade of light, such as the pure white found in some fluorescent sources which have CCT values in the 4000K and above range. LED lighting is available in both of these options, as well as everything in between. This means they can aesthetically enhance virtually any environment or application.

Color Rendering Index (CRI)

The color rendering index, or CRI, is a metric used to determine how well a light source reproduces the colors of an object in comparison to ideal lighting conditions. It has been used to compare the color rendering quality of incandescent, fluorescent, and HID sources for over 40 years. As LEDs are very different from conventional lighting sources, revised color rendering metrics are being developed. However, it is typically agreed on that LED sources with a CRI value of 80+ have good color rendering abilities. The differing quality of LED lighting often results in varying CRI values. To help ensure color quality, one of the Energy Star requirements for LED lighting is to have a CRI value of 80 or above.

Thermal Management

The single most important factor in determining the performance and quality of an LED source is temperature. The thermal stress on LEDs caused by high operating temperatures will: cause a shift in CCT, reduce light output, and significantly shorten life. This is the reason why many of the LED light sources have a large aluminum heat sink integrated in the lamp body, using passive cooling to dissipate the heat generated by the LEDs. It is very important to understand this because applications such as recessed lighting restrict the flow of air around the lamp reducing the performance of passive cooled devices. This is especially true in residential applications where the down light fixture is designed to restrict air flow into the ceiling and the outside of the housing often comes into contact with insulation.

Another consequence of using a large aluminum heat sink is the much increased weight of the LED lamp relative to the incandescent source it is replacing. This may become a significant consideration in use with track lighting where the added weight does not permit the fixture to direct the light due the hinging not being able to support the added weight.

To overcome these problems with passively cooled lamps, there are more advanced thermal solutions that utilize active cooling to not only eliminate the need for the heavy heat sinks, but increase quality and performance. Furthermore, more sophisticated products incorporate thermal sensors that maintain the LEDs within a specified thermal range and compensate for changes in application to ensure product life and maintained performance.

Dimming

LEDs have the ability to be dimmed, but not all LED lighting systems are made dimmable. A product’s dimming capability is often specified on its packaging and/or in its specification documentation. Unlike incandescent sources, the efficiency of LED sources increases as the power is reduced. Hence, the energy savings becomes even greater when LED lamps are used in a dimming application.

However, issues can arise when using LEDs on traditional dimming systems. LEDs operate in a narrow voltage range which is controlled electronically by a power supply incorporated in the light source, whereas incandescent sources operate over the entire range of the supply voltage. This can often cause dimming issues, such as flickering of the LEDs, in certain systems. The more sophisticated products are capable of working on both standard and electronic dimming systems, and manufacturers will typically provide the customer with this information.

Beware of Making Comparison Mistakes With Halogen Lamps

admin — Thu, 03 Mar 2011 15:11:15 +0000

We recently evaluated the Solais LED LR38 (21W, 1000 lumens) against a PAR38 halogen (90W, 130V, 1310 lumens) for a high-profile client. The client had some initial concerns due to the apparent large difference in lumens between the two products, but this was simply because they did not have a proper understanding of the importance behind the 130V rating. After educating the client about how the halogen lamp decreases to 79W and 1000 lumens at 120V (standard line voltage), we realized how common of a mistake this must be in the industry.

Why is this important?
Many commercial applications use 130V halogen lamps and customers assume there is no equivalent LED upgrade because of the high lumen value published for the halogen lamp. Looking deeper into the spec sheets/product literature, one can find the manufacturer’s notes on what the lamp specs will actually be when powered by standard line voltage.

Why does this happen?
There is a very basic electrical formula that states: wattage (W) = voltage (V) x current (I). Halogen lamps heat a metal filament to produce light. In a metal, voltage and current have a linear relationship. This means that when a lamp is designed to 130V but is put onto a 120V system, the wattage will decrease in a linear function (To be completely accurate you need to account for the resistance of the filament, which is a function of its temperature to the 4^th power, but this is not necessary for arguments sake). As the wattage decreases, so does the lumen output.

So why would they design halogen lamps to 130V?
AC voltage is quite unpredictable and can vary depending on geographic location. In a typical 120VAC line, surges or spikes in voltage can occur and a lamp made to 130V will help protect against failures. Additionally, certain regions of the country actually have higher standard voltages (up to 130V). Designing lamps to be 130V is also a common technique used because when a 130V halogen lamp is used on a 120V system, it increases the life of the lamp (In our specific case, the life was increased from 2500 to 5000 hours). Like most things however, there are trade-offs and in this case the lower voltage also reduces the efficacy of the lamp.

What does this really mean?
As a customer there are two key points you must understand for this situation:

1 – If you use 130V PAR lamps, remember that their actual lumen output on standard line voltage is significantly lower than the published specs. This means that high quality, high output LED lamps like those provided by Solais ARE and equivalent upgrade.

2 – When evaluating your energy savings by switching to an LED lamp, especially when it is provided to you by the LED manufacturer, make sure they to account for the correct wattage of the halogen lamps. If 90W (@130V) is used instead of 79W (@120V), more savings will be shown then you will actually receive.

NorthEast hit by another snow storm. Are Solais LED lamps to blame?

admin — Fri, 21 Jan 2011 20:49:55 +0000

As the NorthEast digs out from another snowstorm in a record year, many are starting to wonder if energy efficient Solais LED light bulbs are to blame. “It’s true that Solais products use significantly less energy, and therefore generate less heat than the incandescent bulbs they typically replace,” said James Leahy, CEO of Solais, “but it is too early to tell if recent weather patterns are a direct result of the rapidly increasing adoption of our products.”

“We are cooperating fully with our peers at the National Oceanic and Atmospheric Administration”, said Dr. Steve Johnson, CTO of Solais Lighting, “and will share the results with the public as soon as they are available. In the meantime we encourage people to continue to save massive amounts of energy by purchasing our products.”

Solais urges the public to remember that while the above is meant to be funny, global climate change and energy consumption are very serious matters. LEDs, such as those used in Solais LED lamps, are a new white-light source with the potential to change the way we live and the rate at which we consume energy.

When this clean, energy-efficient technology realizes its full potential:

• Worldwide electricity consumption due to lighting will decrease by more than 50 percent, and total consumption of electricity will decrease by more than 10 percent.

• Carbon emissions and new capital infrastructure associated with electric power generation will decrease proportionately.

• Hazardous waste in today’s conventional light sources, such as fluorescent and HID lamps, will be eliminated.

LED vs. CFL Light Sources

admin — Mon, 20 Dec 2010 20:27:42 +0000

Talking about Solais LED lamps vs. CFLs, you have to address more than just lumens. CFLs are a large diffuse light source and have no control over distribution of the light. There is no such thing as a CFL spot light, because they cannot get a narrow and controlled beam. To properly control a diffused light source such as halogen, fluorescent or HID, the size of the reflector required is a function of the size of the source.

Halogen Lamps
Look at a halogen lamp. The actual filament producing light is very small in relation to the size of the reflector. In a CFL reflector lamp, the CFL tubing fills the entire center of the reflector preventing any control over the light output.

This is extremely important when you want a dynamic and interesting lighting effect. Think of a typical office space with linear fluorescent lighting – it is has a very even, boring, light output. It does the job from a functional standpoint, but it is not a very interesting lighting scheme. This is because they lack any center beam candle power.

Now think of a typical museum with halogen sources. There are different levels of lighting throughout the space (one level of brightness general light on the floor, one level of brightness general light on the wall, one level of brightness focused light on the artwork, etc). This makes for a very interesting space that is nice to be in.

Additionally, although very efficient on their own, CFLs lose a great deal of efficiency when used in a recessed can or any fixture that attempts to control the light output (see image below).

When general illumination is the only intention (the wall, floor, and all interior objects are lighted the same level in a uniform manner), CFLs and fluorescent sources are perfect. When a dynamic lighting effect is desired (the floor has a different brightness from the walls, which is different from the objects in the room, which is different from the accented objects such as paintings), CFLs and fluorescents are the worst choice. This is why many high end homes never use CFLs and have been staying with halogen. People do not want their homes looking like office spaces, hospitals or anything resembling an institution.

LEDs are the first light source that can attempt to do so.

Benefits of LED Lighting

admin — Wed, 15 Sep 2010 17:22:15 +0000

LEDs have taken the lighting industry by storm. It seems like everyone has their focus on LEDs; manufacturers aim to release the next best LED products, designers work to find new ways to utilize LEDs, environmentalists implement LEDs to get the greatest savings, and even artists use LEDs to develop new forms of expression. Although this can sometimes become slightly overwhelming, you should not expect it to subside because LEDs offer tremendous benefits over conventional lighting technologies and their advancements progress further every day. The most significant of these benefits is their efficiency, life, and versatility.

Energy- and Cost-Efficient
The U.S. Depart of Energy has established a goal to reduce electric lighting consumption by 50% before year 2025. Quality LED systems are uniquely positioned to help accomplish this goal because they produce equivalent light output to fluorescent and incandescent sources, but use significantly less wattage.

When this goal is reached, the total global consumption of electricity would be reduced by 10% and CO2 emissions would drastically lower. Also unlike fluorescent and HID sources, LEDs meet RoHS (Restriction of Hazardous Substances) requirements by not incorporating known hazardous compounds such as lead and mercury.

Currently, LEDs consume 25% of the wattage that incandescent sources consume, and 50% of the wattage consumed by compact fluorescent sources. This means that the utilization of LED systems will reduce energy costs by 50 – 75%.

Additionally, the useful life of current LEDs is approximately 10 – 20x longer than that of incandescent sources and 2 – 5x longer than compact fluorescent sources. This results in less frequent lamp replacement, thereby reducing re-lamping and maintenance costs. Despite the higher upfront/initial cost of LED lamps, the extensive energy savings result in rapid payback on these systems.

Life
The proper way to describe LED life is by how long the chips remain useful because they do not typically fail, but rather degrade over time. Quality white LEDs lamps have a useful life typically in the 20,000 – 50,000 hour range depending on the application. This greatly exceeds the life of incandescent sources, which typically burn out within 2500 hours, and CFL sources that typically burn out within 10,000 hours.

Rugged Versatility
Another benefit to LED lighting systems is that they are highly resistant to shock and vibration. In incandescent systems, there are suspended filaments and glass enclosures that are susceptible to breakage, and fluorescent and HID sources are gas-filled/vacuum-sealed and require careful handling. LEDs do not have any of those sensitivities and operate more effectively in cold conditions. These features make LED systems ideal for a broad range of applications such as automotive, traffic, refrigeration and commercial/industrial lighting.

Also unlike incandescent sources, the light emitted from LED systems does not contain harmful ultraviolet or infrared wavelengths, which can be very damaging to art, museum artifacts, retail merchandise, and grocery produce. This, along with the slim profiles and minimal space requirements of LED systems, affords tremendous versatility and advantage in a broad range of potential applications.

This is the basic information regarding the benefits of LEDs. For more detailed information please refer to the Solais LED White Paper under the “downloads” section of the website.

Challenges of LED Lighting

admin — Tue, 14 Sep 2010 22:09:51 +0000

Although LEDs have been a tremendous breakthrough in the advancement of lighting technology, they aren’t perfect, and anyone who says they are is being extremely misleading. LED lighting does provide numerous benefits and advantages over conventional lighting technologies, but it still has its own obstacles to overcome. The good news is that LED lighting is still a very new technology that undergoes tremendous progress every day and substantially betters the challenges it faces. Let’s take a look at what these current challenges are.

Thermal Management
Arguably the greatest challenge to overcome in LED lighting is thermal management. The single most important factor in determining both spectral and electrical system performance of an LED is the “junction temperature.” Junction temperature is the temperature at the junction between the diode’s positive and negative layers.

As electricity passes through the diode, thermal energy builds up at this junction. High junction temperatures will cause the system to have less light output and create a color shift towards resulting in longer wavelengths of light being emitted. This is why thermal management systems in LEDs (heat sinking, active cooling, etc.) are essential to maintaining the maximum expected useful life.

Currently, the most common approach to thermal management for commercially available LED systems is through the use of heat sinks. Heat sinks are the generally finned metal encasements that conduct accumulated heat away from the LED. In low-output applications, such as Gimbal Ring track lighting and other open-air accent lighting, heat sinks are a viable solution.

For high-output applications however, the required heat sinks can become very large in size and weight, which will greatly restrict the application versatility. Additionally, many high-output applications, such as recessed downlights for general lighting, require the lamp to be in an enclosure. This is also troublesome for heat sinks because the limited air movement will reduce their effectiveness at heat dissipation, creating greater heat build-up around the diode that will lower the light output and shorten the useful life of the system. Therefore, it is important to consider the intended application of the LED when choosing between the different thermal management systems.

Another method of thermal management is active cooling. Active cooling thermal management systems incorporate small low-speed fans or impulse coolers into the product. This is an effective, but uncommon approach to thermal management in LED lighting.

Many common high-end electronic devices (computers, televisions, stereo systems, processors, etc.) utilize active cooling systems as their primary cooling solution. As LEDs are also electronic devices, the use of active cooling for LED systems is a logical evolution in design. The components used in active cooling have long life, and when coupled with the overwhelming benefit of continuous cooling on the functioning and life of the LED system, make active cooling the ideal thermal management system in high-output applications. Actively cooled LED systems also have an advantage over heat sink approaches in that they do not add significant bulk or excessive weight, thus maintaining broad application versatility. At Solais, we have used the advances in active cooling to develop our patent-pending Luxiance^TM Technology.

Glare and Brightness Levels
High-Power LEDs emit large amounts of light from extremely small sources. This has the potential to result in a high perception of brightness, so LED products should have proper shielding. Glare can be easily controlled using quality lenses and optics.

System Efficacy
A great deal of the light produced by an LED, approximately 60%, remains trapped inside the diode due to various internal reflection factors. There already are, and continue to be, advances in LED packaging technology that have allowed for increased extraction efficiency. In the near future it is expected that LEDs will reach 150 lumens per watt, which will put LED technology at the forefront of system efficacy among all other lighting technologies.

This is the basic information regarding the challenges of LEDs. For more detailed information please refer to the Solais LED White Paper under the “downloads” section of the website.

LED Industry Standards – What you should know!

admin — Thu, 09 Sep 2010 18:28:33 +0000

LED lighting is inherently different from conventional incandescent, fluorescent, and HID sources. This means that many of the industry standards and guidelines in place to regulate lamp and luminaire production are not applicable to LED systems. As a result, there has been a great deal of variation in the quality of the LED products being put on the market.

Currently, the US Department of Energy (DOE) is working closely with the American National Standards Institute (ANSI), the Illuminating Engineering Society of North America (IESNA), the Alliance for Solid-State Illumination Systems and Technologies (ASSIST), Energy Star, the Federal Trade Commission (FTC), the International Commission on Illumination (CIE), and other organizations to develop such standards (described below). These recommendations and guidelines for LED performance testing continually raise the quality of commercially available products.

LM-79 & LM-80 Testing
When it comes to LED performance testing, the two main standards are LM-79 and LM-80 developed by the IESNA. LM-79 specifies procedures for measuring electrical and photometric data such as total lumen flux, electrical power, efficacy, and other factors. It is a requirement of luminaire for LED-based products incorporating control electronics and heat sinks.

LM-80 specifies procedures for determining the lumen depreciation of LED light sources, arrays, and modules only. It is not applicable to luminaires and it does not provide any methods for estimating useful life beyond the testing period.

Determining the actual useful life of LED products has been a very troublesome procedure to regulate. Since most LED products claim useful life well over 20,000 hours, it does not make sense to force full life testing before products can be sold because 20,000 hours would be almost 2.5 years of 24/7 testing. In an effort to prevent costly full life testing that would prevent smaller companies from helping to develop LED technology, the IESNA is currently developing a new standard, the TM-21. TM-21 will provide a method for determining the expected useful life of an LED luminaire or replacement lamp based on the initial LM-80 data.

ASSIST
ASSIST has developed useful life ratings for two main application types: general lighting and decorative lighting. General lighting applications have a rating of L70, where the end of life occurs when light output drops below 70% in over 50% of the product population. Decorative lighting applications have a rating of L50, where the end of life occurs when light output drops below 50% in over 50% of the product population.

Energy Star
In a world of ever increasing environmentally conscious products, the Energy Star label seems to show up everywhere. For LED lighting however, Energy Star has raised the bar even further, developing very strict efficiency, quality, and lifetime criteria.

Lighting Facts Label
The lack of industry standards has led to tremendous amounts of confusion for consumers in researching the best quality products to purchase. To address consumer confusion, the FTC has established standard labeling requirements that display the most pertinent lighting information uniformly among all products, allowing for easy comparison. One such requirement is the “Lighting Facts” label, analogous to the Nutrition Facts label on food, which lists in a common format factors such as output (in lumens), estimated energy costs, efficacy, life, correlated color temperature (CCT), color rendering index (CRI) and energy used (wattage).

This is the basic information regarding the Industry Standards for LED lighting. For more detailed information please refer to the Solais LED White Paper under the “downloads” section of the website.

Differentiating Between LED Products of Varying Quality Can be Difficult

admin — Tue, 24 Aug 2010 22:05:36 +0000

One of the most frustrating things with LEDs is that the LED lighting market is flooded with products of varying quality, and differentiating between them can be difficult. When consumers are taken by manufacturers producing low quality lamps, it causes distrust in all of LED lighting and affects the implication of the quality products.

In determining which product is best for a desired application, there are a number of factors that should be taken into account including useful life, lumen output, intensity distribution, CCT, and CRI. Although some, if not all, of these performance characteristics may sound familiar to consumers who have researched/purchased lighting before, their use by LED manufacturers can sometimes be misleading. The following is what you need to know about these metrics when associated with LEDs.

Useful Life
Claims of long life can be very misleading because there is a significant difference between the life of a diode and the useful life of an LED system. In a laboratory, under ideal and controlled operating conditions, a single LED diode has the potential to last 100,000 hours or more. However, when this diode gets packaged in an array, connected to other electronic components, sealed inside a lamp housing, and installed into a fixture for a specific application, the useful life is drastically shorter because the diode is more susceptible to electrical overstress and high temperatures. Quality white LED lamps currently on the market typically have a useful life between 20,000 and 50,000 hours.

A major factor influencing actual useful life of an LED system is the lamp’s application. The most common application that shortens useful lamp life is recessed lighting. The two classifications for recessed lighting are type IC installations and type non-IC installations. Type IC installations are those where the housing is in direct contact with insulation. In this type of housing, the potential for temperature build-up is greatest and therefore LED useful life is reduced the most. Type non-IC installations are those where the housing is not in direct contact with insulation and has a 3” clearance from any nearby insulation. This type of housing allows for some ventilation, which helps to reduce temperature levels and maximize LED useful life. However, in most instances even the type non-IC installations will reduce LED useful life more than any open-air type of application. These classifications are very important when choosing an LED PAR Lamp since they are typically used in recessed lighting applications.

Lumen Output and Intensity Distribution
High output applications require a large number of lumens in a uniform distribution pattern. Two lighting characteristics, lumen output and intensity distribution, should be used together to determine the quality of an LED replacement lamp. Manufacturers who provide lumen output but attempt to keep the intensity distribution hard to obtain should be questioned because alone, these values can become very misleading.

An incandescent lamp will typically have a symmetrical circle distribution of the light with the brightest area being in the center and a relatively even drop in brightness out toward the circle’s perimeter. Low quality replacement LED lamps may have oblong or non-circular distributions or even be completely washed out. In order to choose a proper replacement lamp, it is important to know its center beam candlepower (CBCP, which expresses luminous intensity), intensity distribution curve, and lumen output. High quality LED lamps use quality optical components and high performance thermal management systems to provide equivalent values to these characteristics in incandescent sources.



Correlated Color Temperature (CCT)
Choosing the correct LED replacement for an incandescent lamp also requires choosing an LED of a comparable CCT. Incandescent lamps typically have CCTs between 2700K and 3000K, emitting very warm light. The way some manufacturers mislead consumers in claiming incandescent equivalency is by matching the lumen output of an incandescent source, but having higher CCTs (over 4500K). This is because it is easier (and cheaper) for LEDs to produce high output levels in high CCTs than in low CCTs. These high CCT values result in a very cold and sterile feel, unsuitable for replacing most incandescent lighting.

Color Rendering Index (CRI)
The CRI metric is used to determine how well a light source reproduces the colors of an object in comparison to ideal lighting conditions. It has been used to compare the color rendering quality of incandescent, fluorescent, and HID sources for over 40 years. Because LEDs produce light differently from these conventional sources, the International Commission on Illumination (CIE) does not recommend the use of CRI testing for white LEDs.

In some cases, LED lamps with lower CRI values still produce quality white light. For LED lighting, revised color quality testing metrics are still under development; in the meantime, comparison of CRI values should be done cautiously. When possible, the color rendering of an LED source should be evaluated in person and preferably in the context of the intended application.

This is the basic information regarding the what to look for when purchasing LED lighting. For more detailed information please refer to the Solais LED White Paper under the “downloads” section of the website.

Understanding LED Lamp & System Characteristics

admin — Mon, 09 Aug 2010 14:28:42 +0000

LED lighting has numerous characteristics that make it unique from conventional incandescent and fluorescent light sources. Understanding these characteristics and the technical capabilities of the technology will help one understand the true potential of LED lighting.

Another difference with LEDs is they provide directional light, whereas incandescent and fluorescent sources generate a diffuse glow and typically require metal reflectors to control the light distribution. Minimizing the need for reflectors and other optics allows for greater control over and potentially more even light distribution, and enhances efficiency while dramatically increasing the range of potential applications.

Dimming
LED sources potentially have a full dimming range of 100% light output to 0% light output and require no re-strike time. Also, because there is no filament, gas, or plasma being heated to produce light, dimming is immediate. The problem is that most currently available LED lamps are not capable of dimming with standard line-voltage incandescent dimmers because driver limitations. At Solais Lighting however, we have developed a patented pre-load dimming system that allows for full 100%-1% dimming in conjunction with virtually any 2-wire, phase-controlled dimmer. This is significant because it is the only product on the market with this capability.

Lighting Quality
LEDs are inherently monochromatic light sources and therefore do not produce true white light. In order to produce white light, they employ one of two methods: color mixing or phosphor coating.

In color mixing, three separate LEDs (1 Red, 1 Green, and 1 Blue) are packaged together. The mixing of the 3 primary colors is what renders white light. The difficulty of this system is in keeping the output ratio of the different colored die to remain balanced, as high temperatures and time degradation can easily result in noticeable color shifts in the resulting white light. In certain applications, color mixing LED systems provide an exciting flexibility to the space because they can be controlled to provide virtually countless color combinations in addition to white light.

In a phosphor system, an LED that emits short wavelengths (most commonly blue) is enclosed by a lens coated with a phosphor to produce white light. Slight variations in emitted wavelengths will interact differently with the phosphor coating and yield different color temperatures of white light, so the process of “binning” must be used to ensure color uniformity. This process is used to test and sort individual LEDs based on three major characteristics: light output, color, and forward voltage. Phosphor systems are best for general illumination applications where only white light is desired because they have better uniformity than color mixing systems.

This is the basic information regarding the characteristics and capabilities of LEDs. For more detailed information please refer to the Solais LED White Paper under the “downloads” section of the website.