LEDs are indispensable in image processing. Until the development of LEDs, there have been many different forms and technologies applied to lighting.

Understanding the principles and characteristics of light emission will help you test more stably. This article introduces the history of lighting from its inception to the present.

History of light (Lighting)

From the bright sunlight to the poetic moonlight, ancient people used this natural light as the only lighting method to sustain life. Over time, artificial lighting techniques were available to turn the dark night into additional living hours, including open fires, torches, fans, and candlelight.

Later, a number of different lights appeared one after another. Oil lamps provided people with bright light conveniently replacing the original light sources of fire and torches. Next came gas lamps and electric lamps, which were put into practical use during the Industrial Revolution. Because of these technologies, there was a battle for market dominance between gas and electricity.

The History of Lighting: From Open Flames to LEDs

From Arc Lamps to Incandescent Lamps

People were fascinated by the carbon arc lamp, an early form of electric lighting that provided “daylight-like” light. Thomas Edison then invented the incandescent lamp (a carbon bulb, which emitted yellow light), followed by the smaller and brighter tungsten bulb (which emitted white light). Edison then used Japanese bamboo as the filament for the carbon bulb, while a high-melting-point metal filament was used for the tungsten bulb.

The tungsten bulb was followed by two Japanese individuals: Junichi Miura and Kitsuzi Fuwa. Miura invented a coil structure that arranged the filaments in a spiral configuration. Fuwa succeeded in making a frosted glass bulb that diffused and softened the light (frosted inside). The high efficiency and quality of lighting boosted the demand for electric lighting.

Development of electric lamps: arc light, carbon bulb, tungsten bulb

The Fluorescent Era

The dominance of incandescent lamps in the lighting market was replaced by fluorescent lamps. After being developed in 1938 by an American engineer named George E. Inman, the recognition of fluorescent lamps increased. At that time, fluorescent lamps worked by converting ultraviolet light (invisible light) produced by an electric discharge between two electrodes in mercury vapor into visible light through a fluorescent material coated on the inner surface of a glass tube. Later, the elements used in this process were changed from mercury to metals with high luminous efficiency, but the basic principle of light emission remained unchanged. The “energy-saving, white and bright” fluorescent lamps spread rapidly in the 1960s.

While oil lamps, gas lamps and incandescent lamps emitted light by generating heat (thermal radiation), fluorescent lamps used discharge luminescence. This is how the fluorescent era began.

The mechanism and method of emission of light of the first fluorescent lamp

The Shift from “Quantity” to “Quality”

After fluorescent lamps satisfied the demand for “quantity” in the lighting market, the focus shifted to “quality”. In addition to round and straight lamps, other types were developed such as the three-wavelength light emitting type.

This type of light allows both high luminous efficiency and high color rendering properties while maintaining a compact lamp with low power consumption.

The pursuit of high-quality lighting has also been observed in other (non-fluorescent) fields. HID (high-intensity discharge) lamps can emit light dozens of times brighter than fluorescent lamps and are commonly used for outdoor lighting, including streets, roads, buildings and ball fields. In addition, in the field of incandescent lamps, high-efficiency, long-life halogen and krypton lamps have been developed. Incandescent lamps are considered to be the most similar artificial light to sunlight. Their warm colors are effective in stimulating appetite and creating a relaxing atmosphere.

Different shapes of light sources

The Emergence of LEDs

LEDs (Light Emitting Diodes) are the next generation of lighting systems that are more energy efficient than incandescent and fluorescent lamps. LEDs consist of two types of semiconductors, P (positive) and N (negative), and are designed to emit light when an electric current is passed through them. Red and green LEDs have been used since the 1960s, and high-intensity blue LEDs appeared in 1993. The development of white LEDs followed in 1996, creating a wide range of applications.

LEDs are mainly divided into package and chip types. The package type emits a straight light (bright when viewed from the front) while the chip type diffuses light horizontally. The former is commonly used for traffic lights and the latter for backlighting of mobile phone LCD screens. In addition to these types, there are also flat types with a good balance of directivity and diffusion. LEDs have various advantages, including low power consumption, long life cycle (about 40,000 hours), low CO2 emissions, and light-emitting elements as small as a grain of rice. These advantages also make LEDs suitable for reducing the size and weight of items. Furthermore, LEDs are environmentally friendly due to their low UV and IR emission.

Mechanisms and features of different light sources

Types and features of light emitting diodes

Future Lighting Forms: LED, Electroluminescence & Natural Light

The future of lighting will not only be developed using LEDs, but also organic EL (Electro Luminescence). EL is a panel-type light source that provides surface illumination, unlike LEDs which are point sources.

Due to its lightweight and bendable properties, its applications have been expanded to areas such as paper and electronic displays. In the future, luminous walls and ceilings are also expected to be developed.

Advances have also been seen in solar lighting systems that effectively utilize natural light, the source of illumination. Natural light is considered the optimal clean energy to create a comfortable illuminated space. Increasing attention is also being drawn to the synergy between modern “photonic technology” such as LEDs, organic EL and laser beams.

Organic EL (Electroluminescence) Mechanism