Signal lights in cars

A conventional passenger car signal light basically consists of three assemblies: The bulb holder, the housing, and the cover lens.

• The bulb holder positions one or more light sources correctly in relation to the optical system of the light.

• The housing contains the reflectors which are usually molded.

• The cover lens is responsible for light distribution through additional patterned structures.

In order to meet the photometric requirements, the light from the light sources has to be collected and directed, deflected, and distributed. Several optical component parts are used for this purpose.

All the functions in a rear light only work on one brightness level, no matter whether they are switched on during the day, at night, or on a bright foggy morning. The only current possibility of adapting the lights to adverse weather conditions is the rear fog light. This is often used incorrectly, however, and leads to irritation. There is no additional information conveyed about whether the brakes are only being applied lightly or slammed on, for example.

Thanks to ASIGNIS®, the individual signal lights in a rear combination lamp (brakes, direction indicator etc.) can be adapted to the current situation. Depending on weather and visibility conditions the light intensity of the signals (e.g. brighter during the day and darker at night or with the braking signal) can be varied.

The requirement for differing braking signals can either be met by means of a larger signal area, an increase in brightness, or the addition of an increased flashing frequency. The stop light is activated in three stages dependent on deceleration: The greater the deceleration, the more LEDs light up. In the case of a hard stop, one part-array of the red stop light flashes as an additional warning function.

In many vehicles, the light sources are controlled via pulse width modulation (PWM). This has several advantages for the vehicle lighting. For one thing, the same bulbs can be used for different functions, and the service life of the bulbs is increased.

The rear lamps of the Golf V also use PWM. PWM allows the use of a 21 W bulb both for the stop light and for the tail light. The pulse width is modulated in such a way that the 21 W bulb has almost the same luminous flux as a 5 W bulb. If the brake is now actuated, the turn-on time is so long, that 13.5 V is present at the stop light, and the 21 W bulb provides the full luminous flux (see illustration). Once the brake is released again, the voltage returns to 5.74 V.

When replacing bulbs in signal lights, the information and specifications of the manufacturer must always be adhered to. If an incorrect bulb is used, there is the danger that the required luminous intensity will not be reached.