The structure of modern automobile lamps is becoming more and more complicated, at the same time the function is being improved gradually. The development of automobile lamps has experienced four stages.
The first generation of automotive light source is fuels (candles, coal oil or acetylene). These fuels burn to emit lights. Fuels can only satisfy the requirement of early stage automobile lamps due to its low luminous efficiency, weak light intensity, unstable performance, complex operation and etc. shortcomings.
The second generation of automotive light source is incandescent lamp. Incandescent lamp was invented by Edison in 1879. In the year 1913, Americans for the first time apply incandescent lamp in Cadillac cars to act as headlamps. From then on, automobile lamps have undergone a series of revolutionary reformations and the automotive illumination has entered the electric age. Following that, new technologies like reflector, starter, generator and storage battery were invented successively. It was not until the year 1925 that the automobiles adopted incandescent lamps widely. In 1950s, halogen tungsten lamp was invented and quickly become the dominating light bulb for automotive strong light source.
The third generation of automotive light source is HID (high intensity discharge). Be provided with advantages of high luminous efficiency, high brightness and high reliability, HID has replaced incandescent lamp and halogen tungsten lamp to become a new choice for automotive light source.
Now comes the fourth generation of automotive light source —— LED. LED is a kind of semiconductor products with PN junctions. When a positive bias was imposed on the two ends of the PN junctions, the PN junction system was activated, and the carriers will shift from low state of energy into high state of energy. On this condition, unstable carriers in high state of energy will return to low state, thus generates superfluous energy which will be released in the form of photons, according to the conservation of energy principle. That is LED’s illumination principle. Unlike earlier stages light sources, LED doesn’t shine light because of temperature rising caused by heat energy. In LED, the electric energy is switched into light energy directly. The wavelength of the light irradiated by LED is decided by the carriers’ energy difference between low state and high state.
The application of LED in inner automobile light source is becoming wider. It is widely used as accessorial illuminating lamps, backlight of instrument panel and so on in particular.
The five basic components for LED automotive headlamp are: LED array, reflector, lens, radiator, and driving circuit.
The development of LED automotive light source is in direct association with the development of LED products. Only when LED illumination technologies make advancements can LED be more widely used as automotive headlamps. In the near future, with the improvement of LED quality and the reducing of prices, LED products will bring on a new revolution in the illumination domain, which will further influence the transformation of automobile lamps.