Improving Visibility with DLP® Headlights

Automotive manufacturers are seeking methods to enhance nighttime driving visibility. DLP® automotive technology, applicable to headlights, can improve visibility and support other applications.

 

Headlights are used to illuminate the road ahead and enable drivers to identify any potential hazards. 

 

Conventional headlights typically consist of two modules: low-beam lamps and manually operated high-beam lamps. 

 

However, drivers rarely encounter situations that necessitate the use of high-beam headlights, resulting in infrequent utilization of this option.

 

In recent times, there has been a significant push within the automotive lighting industry to enhance the functionality of vehicle headlights and driver visibility, leading to the development of Adaptive Driving Beam (ADB) headlights. 

 

The ADB system automatically controls the entire headlight system, including high beams, allowing drivers to focus on the road without the need to manually switch the high beams on or off based on lighting conditions or the presence of oncoming vehicles.

Advantages of Adaptive High-Beam Headlights

Enabling segmented illumination with high-beam headlights maximizes the amount of light projected onto the appropriate sections of the road.

 

Example of Headlight Illumination

Demonstrating the versatility of DLP technology for high-resolution headlights and how DMD enhances vehicle lighting systems.

 

Future-oriented Headlight Applications

Structural lighting, adaptive traffic sign dimming, and weather detection are just a few new applications where DLP technology adds value and enhances vehicle functionality.

Recently, there has been a significant push within the automotive lighting industry to improve the functionality of vehicle headlights and driver visibility, leading to the development of Adaptive Driving Beam (ADB) headlights. 

 

Advantages of ADB and Resolution

The goal of the Adaptive Driving Beam (ADB) automotive exterior lighting system is to maximize the amount of light projected onto the road while minimizing the impact on oncoming drivers, thereby enhancing road safety.

 

For vehicles without the Far-Beam Field of View (FOV) segmentation (also known as pixel high beams) feature, the ADB system functions by automatically turning the high beams on and off. 

 

New technologies, including DLP technology for automotive applications, enable segmentation of the far-beam headlights' FOV, meaning that individual regions of the high beams can be independently turned on or off.

 

For example, if the far-beam headlights have 12 regions, only a few of these regions need to be turned off to prevent glare for the oncoming drivers. 

The remaining regions can still illuminate the road, resulting in more light generated compared to vehicles without the ADB system.

 

The more regions there are in the ADB system, the more light the far-beam FOV can emit to illuminate the road. 

This relationship holds true as the number of regions increases in magnitude within a constant FOV. 

 

As the regions become smaller, the ADB system can illuminate more areas without affecting other vehicles or causing glare to other drivers.

 

In addition to providing more light on the road, another benefit of increasing the number of regions is smoother movement of the masked areas, reducing interference for the driver caused by rapid switching of a large far-beam FOV. 

 

The masked areas in the ADB system are the FOV regions that are not illuminated by the high-beam modules, preventing glare for oncoming drivers and the ADAS systems of their vehicles.

 

Original Equipment Manufacturers (OEMs) and primary headlight suppliers have been discussing the need to improve ADB resolution to illuminate more details on the road and minimize the interference caused by the movement of masked areas for the driver.

 

The DLP5533A-Q1 high-resolution digital micro-mirror device (DMD) for headlights features 1.3 million individually addressable micromirrors, providing an extremely high ADB resolution. 

 

Each micromirror on the DLP5533A-Q1 corresponds to a region in the far-beam FOV, enabling the ADB system to operate with maximum efficiency and generate highly precise masked areas.

 

Another advantage of DLP technology for automotive applications is the ability to discretely move the masked areas within the far-beam FOV. 

 

With higher-resolution ADB systems and smoother transitions of masked areas within the far-beam FOV, drivers will find these ADB systems to be more natural and less intrusive compared to ADB systems with fewer far-beam regions.

 

OEMs and primary headlight suppliers are exploring the projection of DMD in the headlight FOV to support applications beyond high-resolution ADB headlights.

Headlamp FOV Matrix and DMD

In standard vehicles without an ADB (Adaptive Driving Beam) system, the near-beam area and far-beam area are separated using two modules. The FOV of a standard far-beam module is 40 degrees by 10 degrees for each headlamp.

 

These modules, when aligned, collectively cover an 80-degree by 10-degree far-beam FOV for the vehicle. 

 

Basic ADB systems utilize a limited number of pixels (typically 12 pixels per headlamp, totaling 24 pixels) to control the entire 80-degree by 10-degree far-beam space.

 

Typically, these ADB systems lack control functionality in the vertical region, which means that one zone covers the entire 10-degree range vertically. 

 

With increasing resolution, ADB systems leverage a 2D pixel matrix to achieve far-beam zoning, thereby enabling vertical control and maximizing the amount of light projected onto the road.

OEMs and tier-one headlamp suppliers have been seeking higher-resolution solutions for ADB systems, particularly in the center of the far-beam FOV. 

 

Since road hazards are often directly in front of the vehicle, the center of the far-beam FOV is crucial for significantly increasing the amount of light. 

 

Current automotive headlamp far-beam module illumination distributions typically have a smaller peak brightness area near the center.

 

A novel headlamp design with a third module has been developed by a tier-one headlamp supplier, which provides high resolution only in the center of the vehicle's FOV. 

DLP automotive technology enables a cost-effective high-resolution region, directly addressing the architectural challenge of this new headlamp design, while also enabling the tier-one headlamp supplier to easily create modular designs and support various vehicle trims.

 

The DLP5533A-Q1 DMD, optimized to support a 14-degree by 7-degree FOV module, is commonly used in each headlamp. 

 

However, two DLP5533A-Q1 modules (one per headlamp) can generate a high-resolution area of 28 degrees by 7 degrees for the vehicle's FOV.

 

In addition to providing ADB support (high-resolution area within the far-beam FOV), this cross-functional capability allows DLP headlamp modules to project high-resolution symbols onto the "HR graphic region" within the near-beam FOV.

 

Due to the DLP5533A-Q1's ability to provide the required resolution for creating legible symbols, such as a right-turn arrow indicating the need for a right turn, the device is well-suited for symbol projection.

 

Due to the directional nature of vehicle headlamps, the relationship between resolution and symbol clarity projected by the headlamps is more pronounced compared to standard projection displays. 

 

As the headlamp projections are not performed on a surface perpendicular to the projection source, the projected symbols are prone to elongation, making it difficult for the driver to comprehend them without sufficient angular resolution.

 

The difference in projected symbols between a resolution of 0.05 degrees per pixel (achievable through a dedicated 20,000-pixel matrix for symbol projection) and a resolution of 0.01 degrees per pixel (achievable through the near-beam area of the DLP5533A-Q1 high-resolution headlamp module) becomes apparent. 

 

These angular resolutions correspond to approximately 12 lines and 49 lines when projecting a 2-meter-high image from a distance of 10 meters.

The symbol projection area can assist the driver in navigating to the destination, warning about potential hazardous road conditions, or projecting the planned path of the vehicle. 

 

Symbol projection not only offers an alternative means of vehicle communication but can also serve as a differentiating factor for vehicle functionality and driving experience.

 

Symbol projection showcases the versatility of DLP technology for high-resolution headlamps and how it extends the value proposition of vehicle lighting systems.

 

Future Applications of Headlamp Technology

While DLP technology has greatly improved ADB systems and enabled symbol projection, headlamps based on DLP technology have other methods to enhance Advanced Driver Assistance Systems (ADAS) functionality, adding value to vehicles through expanded applications.

 

These future-oriented applications may include structured lighting (to aid next-generation ADAS in better detecting and recognizing objects and obstacles on the road), traffic sign dimming (to prevent glare on forward-facing cameras), and weather detection (to alert drivers of potential hazardous road conditions).

 

Structured lighting: The DMD can switch states at an extremely fast level in microseconds, allowing DLP headlamp modules to display single-bit patterns in very short durations. 

 

When these single-bit patterns are synchronized with the refresh rate of the vehicle's forward-facing camera, DLP headlamp modules can project patterns intended for depth sensing without drawing the driver's attention. This application is known as structured lighting.

 

The ADAS processor captures the response to the patterns from the forward-facing camera and determines if there are any objects in the vehicle's path. 

 

If the ADAS system detects any debris or potholes, it can warn the driver using the symbol projection feature, indicating potential hazards.

 

In addition to pothole and debris detection, structured lighting can also enhance the performance of active suspension systems at night. 

 

Many active suspension systems perform poorly at night due to poor visibility, but DLP headlamps can significantly improve the performance of active suspension systems.

 

Traffic sign dimming: OEMs and tier-one suppliers are considering relocating the ADAS forward-facing camera sensors near or within the headlamps. 

One drawback of this new position is that the performance of the ADAS camera system may be compromised near nighttime traffic signs. 

 

If adaptive headlamps reflect light directly back to the light source, the traffic signs can interfere with the performance and accuracy of the ADAS forward-facing camera at night.

 

When light shines directly onto the lens of the camera, the camera sensor can experience "blooming" or oversaturation, completely washing out the image. 

This prevents any real-world data from reaching the ADAS system, rendering it unable to warn the driver of potential hazards.

 

Leveraging the high resolution of DLP headlamp modules, the ADAS system can create efficient masks to block and extinguish the light directed towards traffic signs. 

 

This enables the front-end camera of the ADAS system to function properly, allowing the driver to better understand the traffic signs.

Traffic sign dimming becomes essential functionality for ADB when used on urban streets and highways, as traffic signs are frequently encountered on these types of roads.

Weather Detection: High-resolution headlamps can be utilized to assist in detecting weather conditions during nighttime driving. 

 

Some vehicles rely solely on cameras to detect weather conditions during the day, but this becomes a challenge at night due to low light conditions.

 

By leveraging high-resolution headlamps, vehicles can increase the intensity of light projected onto specific areas, thereby enhancing the visibility of the camera. 

 

By enabling the ADAS forward-facing camera system to detect weather conditions at night, vehicles can automatically activate safety features or configurations to better handle hazardous conditions, including foggy weather and icy road surfaces.

 

Conclusion

While the DLP5533A-Q1 DMD is designed to enhance ADB resolution and help vehicles achieve greater road illumination, its 1.3 million micromirrors enable new applications. 

 

Symbol projection can assist drivers by projecting navigation symbols onto the road ahead, helping them keep their focus on the road. It can also facilitate "communication" with surrounding vehicles by projecting predefined paths.

 

Structural lighting enables functions that can warn drivers of imminent dangers such as potholes and objects on the road. 

 

Traffic sign dimming can help reduce glare on forward-facing cameras and support appropriate ADAS functionalities.

 

Weather detection can help drivers keep their attention on the road during critical moments. 

 

DLP high-resolution headlamps will continue to meet the demands of OEMs and primary headlamp suppliers while providing a platform for innovation and the development of new functionalities for design engineers.