Light plays an important role for the cockpit.
Light plays an important role for the cockpit.
( Source: Osram Opto Semiconductors)

interior design LED trends in vehicle interior design

| Author / Editor: Stephan Pawlik * / Florian Richert

Light in automotive engineering is not only LED headlights and exterior lighting. Visible and invisible light also plays an important role in vehicles.

The concept car Snap approaches slowly and projects "Welcome" onto the floor in front of the vehicle door as soon as the passenger approaches and rolls out a virtual red carpet of light. At major automotive and technology fairs such as the CES, the IAA or the Geneva International Motor Show, visitors can see what the future of mobility could look like. Increasingly intelligent and autonomously functioning applications based on visible and invisible light are already ensuring greater safety and comfort in today's vehicle models.

In addition to exterior lighting, this also includes a large number of new applications for vehicle interiors. Advances in the development of optoelectronics play a central role in the implementation of new, dynamic and intelligent light-based applications with LEDs. The first application example shows concept vehicles such as the "SNAP" and "microSNAP" models from Rinspeed already when accessing the vehicle interior.

Applications from the mobile and consumer worlds have accelerated the development of biometric identification systems. From fingerprints to iris scans and facial recognition, biometric procedures are considered to be extremely reliable, secure and user-friendly. Many automobile manufacturers are therefore considering using such systems for secure vehicle access, driver recognition or access to personal data in the vehicle.

Biometric applications and design

Infrared light-based biometric applications such as 3D face recognition or iris scanning ensure that only authorized persons can enter the vehicle. At the same time, however, they can also activate individually desired settings or the use of private data. As soon as a person is recognized by the system, everything can be adapted to the needs of the respective passenger, from the preferred interior lighting or temperature to the seating position or favorite music. The application also offers various advantages for the growing number of Car-Sharing concepts. Thanks to these technologies, users do not have to forego their personal preferences in the vehicle or constantly adjust them.

Overall, light-based applications in vehicle interiors are increasing rapidly. For automotive brands and OEMs, lighting elements are not only an important design element for differentiating themselves from the competition. They also open up new fields of application. This also includes ambient lighting, which has been a fixed design component for a long time. Today, it can already be individually controlled for some vehicle brands and models.

Depending on taste, mood or situation, passengers can adjust the colors. The spectrum ranges from soothing blue or green tones to invigorating yellow-orange or dynamic red. In the future, interior lighting will take on additional functions. It can, for example, change color or dynamically direct a driver's attention back to the traffic. Tasks like these are becoming increasingly relevant in connection with semi-autonomous or fully autonomous driving concepts. However, corresponding dynamic lighting applications require additional control electronics.

Control elements in the vehicle continue to increase. Additional components are also in demand. That's why developers need to have a special eye on installation space, thermal properties, and fuel consumption. An obvious point is the amount of space required when space is very limited.

To accommodate more elements in the same space, the electronic components installed must shrink. These include surface-mountable LEDs, which are a particularly popular variant for developers due to their cost efficiency when mounted on FR4. One example is the Toppled E1608 from Osram Opto Semiconductors: Compared to the predecessor models, the package could be reduced by a factor of 20 for the same performance. Premold technology ensures a robust package.

Minimizing LED and control electronics

The Topled E1608 measures 1.6 mm x 0.8 mm and is 20 times smaller than previous models. This makes the LED package suitable for lighting in vehicle interiors.
The Topled E1608 measures 1.6 mm x 0.8 mm and is 20 times smaller than previous models. This makes the LED package suitable for lighting in vehicle interiors.
(Source: Osram Opto Semiconductors)

The number of LEDs and control elements in the vehicle continues to increase and the number of control elements in the vehicle continues to increase. Additional components are also in demand. That's why developers need to have a special eye on installation space, thermal performance and fuel consumption. An obvious point is the amount of space required when space is very limited.

In order to accommodate more elements in the same space, the electronic components installed must shrink. These include surface-mountable LEDs, which are a particularly popular variant for developers due to their cost efficiency when mounted on FR4. One example is the Topled E1608 from Osram Opto Semiconductors: Compared to the predecessor models, the package could be reduced by a factor of 20 for the same performance. Premold technology ensures a robust package.

Small LEDs and the amount of fluorescent material

The designation E1608 refers to the package dimensions of 1.6 mm x 0.8 mm. A standard toppled currently measures 3.2 mm x 2.8 mm. The height of 0.6 mm is also flatter than the previous 1.9 mm. The compact Toppled thus enables different designs, especially for applications in the interior of a vehicle. In combination with the efficient converters, the low-power LED ensures high-performance values despite its small dimensions. For example, the conversion pure green version achieves a value of 780 mcd at 10 mA.

During miniaturization, the developers faced several problems: for example, the reproduction of minute amounts of fluorescent material and its dosing into a housing with an opening of 0.5 mm. Besides, material combinations in this microscopic range sometimes behave quite differently than on the macroscopic scale.

Dynamic lighting functions thanks to integrated electronics

In addition to three color chips, a driver IC is also integrated into the Osire E4633i. The LEDs can be individually controlled via a serial bus.
In addition to three color chips, a driver IC is also integrated into the Osire E4633i. The LEDs can be individually controlled via a serial bus.
(Source: Osram Opto Semiconductors)

The requirements for dynamic lighting applications are even more demanding. Osram Opto Semiconductors has developed a series of LEDs with three RGB color chips and a serially controllable driver to reduce the number of components for the limited space available and simplify implementation.

In the first stage, a very small RGB LED with a unique identifier was developed on the package. Using this identifier, which is designed as a 2D data matrix code, the user of the LED, which is usually a Tier 1, can read out the stored optical measured values of the light-emitting diode. This saves the otherwise necessary measurement of Tier 1 and simplifies the manufacturing process at the same time.

Together with the very small housing dimensions of 3.3 mm x 2.3 mm x 0.7 mm, this LED is also suitable for longer LED chains. This allows for dynamic lighting functions to be displayed. With the soon available Osire E4633i, the correct calibration of the RGB color chips is already firmly burnt into an OTP.

One ASIC is already integrated in the LED package

Also, a three-channel driver is integrated into the LED, which is controlled via a serial bus. This is made possible by integrating an ASIC into the LED package. With this approach, longer chains equipped with the Osire E4633i can be connected to a serial bus according to the daisy-chain principle. Via this serial bus, each LED can be individually controlled and its diagnosis is also possible. Since the calibration has already been done, the control can be simplified and is limited to one command: Set RGB value.

This fast bus and the small control cycles ensure that longer chains of LEDs can be controlled in real-time and that dynamic lighting functions can be displayed. The Osire family is qualified for the various applications in the automotive industry and the first products have already been launched on the market, others are about to be introduced.

Safety and assistance systems

In addition to the design aspects for the ambient light in the vehicle, the entire display segment is added: head-up displays and augmented reality applications. Also, infrared (IR) applications support important safety and assistance systems such as driver monitoring. Such functions are important, for example, concerning future semi-autonomous vehicles, because the car must be able to alert the driver or give him command in certain driving situations.

Light in the vehicle interior becomes an essential component and takes on important functional and design tasks.

This article was first published in German by Next Mobility.

* Stephan Pawlik works as a marketing engineer at Osram Opto Semiconductors in Regensburg.