Light Technology Basics
About 85 percent of our perceptions come from our eyes, so Lighting is important to what we do because 85 percent of our perceptions come from our eyes. Light can be produced naturally, the way the sun produces light, or artificially as in the case of electrical energy being transformed into light.
This generally occurs in one of two ways; that which comes from Incandescence, in which current passes through a filament then heats and then glows, or gas discharge, in which current passes through a gas. The atoms glow, giving off ultraviolet light, reacting with phosphor to produce visible light.
Incandescent
Incandescent bulbs heat a filament to generate light. We have all been used to lightbulbs. More than ninety percent of the energy consumed by the world at large are from obsolete, but still common, incandescent lightbulbs.
CFL
A compact fluorescent lamp or (CFL), are dubbed as energy saving light. CFLs are less commonly referred to as a compact fluorescent tube (CFT). It is a type of fluorescent lamp.
Many CFLs are designed to replace an incandescent lamp and can fit into existing light fixtures formerly used for incandescents.
Compared to general service incandescent lamps giving the same amount of visible light, CFLs generally use less power, have a longer rated life, but a higher purchase price. Like all fluorescent lamps, CFLs also contain mercury, which complicates their disposal.
This generally occurs in one of two ways; that which comes from Incandescence, in which current passes through a filament then heats and then glows, or gas discharge, in which current passes through a gas. The atoms glow, giving off ultraviolet light, reacting with phosphor to produce visible light.
Incandescent
Incandescent bulbs heat a filament to generate light. We have all been used to lightbulbs. More than ninety percent of the energy consumed by the world at large are from obsolete, but still common, incandescent lightbulbs.
CFL
A compact fluorescent lamp or (CFL), are dubbed as energy saving light. CFLs are less commonly referred to as a compact fluorescent tube (CFT). It is a type of fluorescent lamp.
Many CFLs are designed to replace an incandescent lamp and can fit into existing light fixtures formerly used for incandescents.
Compared to general service incandescent lamps giving the same amount of visible light, CFLs generally use less power, have a longer rated life, but a higher purchase price. Like all fluorescent lamps, CFLs also contain mercury, which complicates their disposal.
The Emergence of New Technologies
Cold Cathode Fluorescent Lamp
Electrodeless lamp, also known as a radiofluorescent lamp or fluorescent induction lamp have no wire conductors penetrating their envelopes, and instead excite mercury vapor using a radio-frequency oscillator.
Currently, this type of light source is struggling with a high cost of production, stability issues since production plants are in China; and problems about establishing internationally recognized standards.
Cold Cathode Fluorescent Lamp (CCFL)
This is one of the newest forms of CFL technologies. CCFLs use electrodes without a filament. The voltage of CCFLs is about 5 times higher than CFLs and the current is about 10 times lower.
CCFLs have a diameter of about 3 millimeters. CCFLs were initially used for backlighting LCD displays, but they are now also manufactured for use as lamps. The efficacy (lumens/watt) is about half that of CFLs.
In terms of advantage, they are said to be instant-on; like incandescents, they are compatible with timers, photocells and dimmers, and they have a long life of approximately 50,000 hours.
CCFLs are a convenient transition technology for those who are not comfortable with the short lag time associated with the initial lighting of CFLs. They are also an effective and efficient replacement for lighting that is turned on and off frequently with little extended use (e.g. a bathroom or closet).
Currently, this type of light source is struggling with a high cost of production, stability issues since production plants are in China; and problems about establishing internationally recognized standards.
Cold Cathode Fluorescent Lamp (CCFL)
This is one of the newest forms of CFL technologies. CCFLs use electrodes without a filament. The voltage of CCFLs is about 5 times higher than CFLs and the current is about 10 times lower.
CCFLs have a diameter of about 3 millimeters. CCFLs were initially used for backlighting LCD displays, but they are now also manufactured for use as lamps. The efficacy (lumens/watt) is about half that of CFLs.
In terms of advantage, they are said to be instant-on; like incandescents, they are compatible with timers, photocells and dimmers, and they have a long life of approximately 50,000 hours.
CCFLs are a convenient transition technology for those who are not comfortable with the short lag time associated with the initial lighting of CFLs. They are also an effective and efficient replacement for lighting that is turned on and off frequently with little extended use (e.g. a bathroom or closet).
Emerging Lighting Technologies
LEDs
LED creates light by electrically stimulating semi-conductor material called a light-emitting diode (LED). It is a light source that emits light when an electrical current is applied to it.
Discovered in the early 20th century, the technology has been greatly developed and continues to advance through research and development. From early indicator lights with low light output -- with only one available color--to today's devices that emit visible, ultraviolet or infra red light, with very high brightness.
The technology behind LED is based on semiconductor technology, which is also the basis of modern computers. In the semiconductor diode, electrons are brought from a state of high energy to a state of low energy, and this energy difference is emitted in the form of light, the effect is called electroluminescence.
Specific colors are associated with specialized materials that are constructed to have an energy gap corresponding to light with particular wavelength/color. An LED is usually a small area (less than 1 mm2) light source, often with optics added directly on top of the chip to shape its radiation pattern and assist in reflection.
LEDs have many advantages to traditional light sources, such as: Low energy consumption, longer lifetime, robustness, small size among others.
However they still remain relatively expensive, and have some characteristics that differentiate them from traditional light sources. LEDs need current- and heat management. These advantages have caused LEDs to be used in many new applications where traditional light sources could not be used, as well as traditional applications where specifically, low energy consumption is appreciated.
Despite high price and the need for specialized designs, LEDs are seeing adoption in more and more areas of lighting.
LED lamps presently have efficiencies of 30% with higher levels attainable. LEDs providing over 150 lm/W have been demonstrated in laboratory tests and lifetimes of around 50,000 hours are typical. For a variety of reasons, the efficacy of available LED fixtures does not typically exceed the efficiency of CFLs.
Operating temperatures are higher than those used to rate the LEDs. The driving circuitry loses some power, and to reduce the cost, LEDs are driven at their brightest, not their most efficient point.
Tests conducted in 2008 of commercial LED lamps designed to replace incandescent or CFL lamps showed that average efficacy was still about 31 lm/W ; tested performance ranged from 4 lm/W to 62 lm/W.
As of 2007, LED lamps have not delivered the intensity of light output required for domestic uses at a reasonable costs.
LED creates light by electrically stimulating semi-conductor material called a light-emitting diode (LED). It is a light source that emits light when an electrical current is applied to it.
Discovered in the early 20th century, the technology has been greatly developed and continues to advance through research and development. From early indicator lights with low light output -- with only one available color--to today's devices that emit visible, ultraviolet or infra red light, with very high brightness.
The technology behind LED is based on semiconductor technology, which is also the basis of modern computers. In the semiconductor diode, electrons are brought from a state of high energy to a state of low energy, and this energy difference is emitted in the form of light, the effect is called electroluminescence.
Specific colors are associated with specialized materials that are constructed to have an energy gap corresponding to light with particular wavelength/color. An LED is usually a small area (less than 1 mm2) light source, often with optics added directly on top of the chip to shape its radiation pattern and assist in reflection.
LEDs have many advantages to traditional light sources, such as: Low energy consumption, longer lifetime, robustness, small size among others.
However they still remain relatively expensive, and have some characteristics that differentiate them from traditional light sources. LEDs need current- and heat management. These advantages have caused LEDs to be used in many new applications where traditional light sources could not be used, as well as traditional applications where specifically, low energy consumption is appreciated.
Despite high price and the need for specialized designs, LEDs are seeing adoption in more and more areas of lighting.
LED lamps presently have efficiencies of 30% with higher levels attainable. LEDs providing over 150 lm/W have been demonstrated in laboratory tests and lifetimes of around 50,000 hours are typical. For a variety of reasons, the efficacy of available LED fixtures does not typically exceed the efficiency of CFLs.
Operating temperatures are higher than those used to rate the LEDs. The driving circuitry loses some power, and to reduce the cost, LEDs are driven at their brightest, not their most efficient point.
Tests conducted in 2008 of commercial LED lamps designed to replace incandescent or CFL lamps showed that average efficacy was still about 31 lm/W ; tested performance ranged from 4 lm/W to 62 lm/W.
As of 2007, LED lamps have not delivered the intensity of light output required for domestic uses at a reasonable costs.
Solid State LEDs
Solid State LED refers to a type of lighting that utilizes light-emitting diodes (LEDs), organic light-emitting diodes (OLED), or polymer light-emitting diodes (PLED) as sources of illumination rather than electrical filaments, plasma (used in arc lamps such as fluorescent lamps), or gas.
* Research information including images in this page were culled from internet resources and as such are copyrighted to their respective owners.
Compared to incandescent lighting, however, Solid State LEDs create visible light with reduced heat generation or parasitic energy dissipation, similar to that of fluorescent lighting. In addition, its solid-state nature provides for greater resistance to shock, vibration, and wear, thereby increasing its lifespan significantly.
Solid State devices such as LEDs are
subject to very limited wear and tear if operated at low currents and at low temperatures.
Many of the LEDs produced in the 1970s and 1980s are still in service today. Typical lifetimes quoted are 25.000 to 100.000 hours but heat and current settings can extend or shorten this time significantly.
The most common way for LEDs (and diode lasers) to fail is the gradual lowering of light output and loss of efficiency. Sudden failures, however rare, can occur as well.
Solid-state lighting is often used in traffic lights and is also used frequently in modern vehicle lights, train marker lights etc., and may compete with CFLs in the near future.
Solid-state lighting has the potential to revolutionize the lighting industry. Light-emitting diodes (LEDs) are commonly used in signs, signals and displays and are rapidly evolving to provide light sources for general illumination. This technology holds promise for lower energy consumption and reduced maintenance.
Efficiency: LEDs produce more light per watt than incandescent bulbs.
Colour: LEDs can emit light of an intended colour without the use of colour filters that traditional lighting methods require.
Size: LEDs can be very small (smaller than 2 mm2) and are easily populated onto printed circuit boards.
On/Off time: LEDs light up very quickly. A typical red indicator LED will achieve full brightness in microseconds. LEDs used in communications devices can have even faster response time.
Cycling: LEDs are ideal for use in applications that are subject to frequent on-off cycling, unlike fluorescent lamps that burn out more quickly when cycled frequently, or HID lamps that require a long time before restarting.
Dimming: LEDs can very easily be dimmed either by Pulse-width modulation or lowering the forward current.
Cool light: In contrast to most light sources, LEDs radiate very little heat in the form of IR that can cause damage to sensitive objects or fabrics. Wasted energy is dispersed as heat through the base of the LED.
Slow failure: LEDs mostly fail by dimming over time, rather than the abrupt burn-out of incandescent bulbs.
Lifespan: LEDs can have a relatively long useful life. One report estimates 35,000 to 50,000 hours of useful life, though time to complete failure may be longer. Fluorescent tubes typically are rated at about 10,000 to 15,000 hours, depending partly on the conditions of use, and incandescent light bulbs at 1,000–2,000 hours.
Shock resistance: LEDs, being solid state components, are difficult to damage with external shock, unlike fluorescent and incandescent bulbs which are fragile.
Focus: The solid package of the LED can be designed to focus its light. Incandescent and fluorescent sources often require an external reflector to collect light and direct it in a usable manner.
Toxicity: LEDs do not contain mercury, unlike fluorescent lamps. Next...
