As an industry insider, when encountering product iterations of different types of lighting fixtures in the industry, some lighting fixture products are gradually phased out and updated in the market, but the name is still used in some product selections. This article will tell you the basic information and evolution process of light sources!
There are three main categories of light emission forms: thermal radiation light sources, gas discharge light sources, and electroluminescent light sources.
Thermal Radiation Light Sources
Thermal radiation light sources include incandescent lamps and halogen lamps. These light sources emit light energy at high temperatures through electric current flowing through conductive objects. Incandescent lamps are common light bulbs in daily life, while halogen lamps are improved incandescent lamps that use halogen elements to extend service life and improve efficiency.
The energy conversion efficiency of incandescent lamps is very low, with only 2% to 4% of electrical energy converted into visible light. However, they have advantages such as good color rendering, continuous spectrum, and convenient use. The tungsten filament of an incandescent lamp heats up under the action of electric current, causing the filament to reach incandescence and emit light. Based on the luminous principle of thermal radiation light sources, a large amount of electrical energy is converted into heat energy, resulting in low luminous efficiency.
Halogen lamps are incandescent lamps filled with gas containing partial halogen elements or halides. In ordinary incandescent lamps, the high temperature of the filament causes tungsten to evaporate, and the evaporated tungsten deposits on the bulb shell, causing the bulb glass to blacken. In 1959, people invented the halogen lamp, which eliminated this blackening phenomenon using the principle of halogen cycle. The halogen cycle further improves the lamp's lifespan, with the color temperature reaching 3200K and the luminous efficiency increasing to 30lm/W. To enhance the lifespan and efficiency of incandescent lamps, halogens are added to the lamp to generate a halogen cycle, which not only reduces the temperature of the tungsten filament, alleviates the blackening of the bulb shell, but also improves lifespan and efficiency, widely used in traditional indoor and commercial lighting.
Advantages of thermal radiation light sources:
1. Small volume
2. Simple structure
3. Low cost
Disadvantages:
1. Large heat dissipation
2. Low luminous efficiency
3. Short lifespan
Applications: Generally used in residential buildings and places where frequent switching is required and stroboscopic phenomena are not allowed, such as the sun, incandescent lamps, halogen lamps, bath heater and etc.
Gas Discharge Light Sources
Gas discharge light sources cover fluorescent lamps, low-pressure sodium lamps, high-pressure mercury lamps, high-pressure sodium lamps, metal halide lamps, etc. These light sources emit light through gas discharge when electric current flows through gases or metal vapors. Gas discharge light sources have high luminous efficiency, long lifespan, and various light colors, making them a widely used category in modern lighting.
Fluorescent lamps (Fluorescent lamps), also known as fluorescent lights. Traditional fluorescent lamps, i.e., low-pressure mercury lamps, emit visible light by using low-pressure mercury vapor to release ultraviolet rays after power-on, so they belong to low-pressure arc discharge light sources.
Low-pressure sodium lamps are electric light sources that emit light through low-pressure sodium vapor discharge. Their glass shell is coated with an infrared reflection film, making them light sources with small light decay and the highest luminous efficiency. Low-pressure sodium lamps emit monochromatic yellow light, suitable for places with no requirements for light color, but their "fog-penetrating" performance is excellent, especially suitable for highway, traffic road, municipal road, park, and courtyard lighting, allowing people to clearly see objects with small color differences. Low-pressure sodium lamps are also an efficient lamp type to replace high-pressure mercury lamps for energy saving, with expanding application scenarios.
High-pressure mercury lamps are high-pressure mercury vapor discharge lamps with a fluorescent powder coating on the inner surface of the glass shell, emitting soft white light with a simple structure. With low cost and maintenance fees, they can directly replace ordinary incandescent lamps, featuring high luminous efficiency, long lifespan, and energy economy, suitable for industrial lighting, warehouse lighting, street lighting, flood lighting, safety lighting, etc. Structurally, high-pressure mercury lamps have an olive-shaped glass shell with a sealed discharge tube inside, containing two opposite metal electrodes and filled with high-pressure mercury vapor. After power-on, a high-resistance resistor first makes the gas in the tube conductive, causing an arc between the two electrodes to heat the gas to a high temperature and emit light. The shell is often coated with fluorescent powder, which can convert part of the ultraviolet light into visible light.
Metal halide lamps (abbreviated as metal halide lamps) are discharge lamps that work with alternating current and generate arc discharge light in a mixed vapor of mercury and rare metal halides. Metal halide lamps are the third-generation light sources made by adding various metal halides to high-pressure mercury lamps. Scandium-sodium metal halide lamps are used for lighting, featuring high luminous efficiency, good color rendering, long lifespan, etc. They are energy-saving new light sources close to daylight color, widely used in indoor lighting of stadiums, exhibition centers, large shopping malls, industrial factories, street squares, stations, docks, and other places.
Electroluminescent Light Sources
Electroluminescence (EL) is a phenomenon, mainly including field-induced light sources and light-emitting diodes (LED). These light sources make solid materials emit light under the action of an electric field, directly converting electrical energy into light energy. Among them, electrons and holes recombine in the P-N junction to produce light; the strong field type involves high-energy electrons colliding to excite luminescent center ions to emit light.
This technology is widely used in display devices, especially OLED, which is regarded as the key to future display technology due to its self-luminescence and low-power consumption characteristics. The lifespan of OLED is a key consideration in its commercialization, affected by various aging mechanisms. Professional systems such as EL-Lab are used to test and optimize the performance and lifespan of electroluminescent devices. LED occupies an important position in modern lighting and display technology due to its high efficiency, long lifespan, and diverse color options.
Light Emitting Diode (LED for short) is a semiconductor electronic component that can convert electrical energy into light energy. It is made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc. When electrons recombine with holes, they can radiate visible light, so it can be used to make light-emitting diodes. LEDs are used as indicator lights in circuits and instruments or form text or digital displays, with wide applications.
Since the first appearance of LED in 1962, it could only emit low-brightness red light in the early stage, and then versions of other monochromatic lights were developed. Today, the light it can emit has covered visible light, infrared rays, and ultraviolet rays, and the brightness has also increased to a considerable level. With the continuous advancement of technology, LED has been widely applied in displays and lighting.