Improve visibility with DLP® headlights-EEWORLD

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Automakers are looking for ways to improve visibility while driving at night. DLP® automotive technology for headlights improves visibility and supports other applications.

Headlights are used to illuminate the road ahead and make the driver aware of any potential hazards. Basic headlights usually use two modules: a low-beam base light and a manual on/off high-beam light. However, drivers rarely encounter situations that require the use of high-beam headlights,
so this option is rarely used.

Recently, there has been a strong push within the automotive lighting industry to improve vehicle headlight functionality and driver visibility, resulting in the development of adaptive high beam (ADB) headlights. The ADB system automatically controls the entire headlights, including high beams, allowing the driver to focus on the road without having to turn the high beams on or off depending on lighting conditions and the presence of oncoming vehicles.

1 Advantages of adaptive high-beam headlights

Enable high-beam headlamp field segmentation to maximize the amount of light projected on the appropriate parts of the road.

2 Example of headlight field of view

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

3 Headlight applications for the future

Structured light, traffic sign dimming, and weather detection are just some of the new applications where DLP technology is adding value and improving vehicle functionality.

ADB Advantages and Resolution

The goal of ADB automotive exterior lighting systems is to increase road safety by maximizing the amount of light projected onto the road without disturbing the driver of oncoming cars. For vehicles without high beam field of view (FOV) zoning (also known as pixel high beam) functionality, ADB system functionality includes automatically turning the high beams on and off. New technologies, including DLP technology for automotive applications, enable the high-beam headlamp FOV to be zoned, in other words, each area of the high-beam headlamp can be turned on or off separately.

For example, if a high-beam headlamp has 12 zones, only a few of these zones need to be switched off to prevent glare for the driver of oncoming vehicles. Other zones can still illuminate the road, and such vehicles produce more light than vehicles without an ADB system. Figure 1 shows an example of a nighttime driving situation in which a driver gradually approaches oncoming vehicles, traffic signs, and potholes in the road. The driver's vehicle is not equipped with an ADB system, so only the vehicle's basic lighting illuminates the road. Figure 2 shows the same driving scenario as Figure 1, but now the driver's vehicle is equipped with a 12-pixel partitioned ADB system. Zoned ADB systems are represented by multiple red boxes that highlight the illuminated area for each pixel in the high-beam FOV.

Figure 1. Headlamp FOV with base lighting module only.

Figure 2. Headlight FOV with 12-pixel matrix. In the high-beam FOV, each pixel is represented by a red area.

As can be seen from Figures 1 and 2, the more partitions in the ADB system, the more light the high-beam FOV can emit to illuminate the road. This relationship also holds true when the number of zones increases by orders of magnitude in a constant FOV - because as the partitions become smaller, the ADB system can light more of the zone without illuminating other vehicles, as well. No glare to other drivers.

In addition to allowing more light to shine on the road, another benefit of adding partitions is that the movement of the shaded area is smoother, which can reduce the interference to the driver caused by the large-area high-beam FOV quick switch. The shielded area in the ADB system is the FOV area that is not illuminated by the high- beam module , which can prevent glare to the driver of the oncoming vehicle and the vehicle's ADAS system. In Figure 2, the occluded areas are the areas in the high-beam FOV that are missing LEDs, represented by red boxes, and these are areas around oncoming vehicles (to prevent glare to oncoming vehicle drivers) and traffic signs (Prevents reflected light from causing glare on the front camera of the ADAS system).

Vehicle original equipment manufacturers (OEMs) and Tier 1 headlight suppliers have been discussing the need for increased ADB resolution to illuminate more detail on the road and reduce driver disruption from movement of obscured areas. The DLP5533A-Q1 high-resolution headlamp digital micromirror device (DMD) features 1.3 million individually addressable micromirrors to provide extremely high ADB resolution. Each micromirror on the DLP5533A-Q1 can correspond to an area in the high-beam FOV, allowing the ADB system to operate at maximum efficiency and produce very precise masking areas.

Another benefit of DLP technology for automotive applications is the ability to move the masked area discretely in the high-beam FOV. With higher-resolution ADB systems and smoother transitions of masked areas in the high-beam FOV, drivers will find these ADB systems more natural and less intrusive than ADB systems with fewer high-beam areas. OEMs and Tier 1 headlamp suppliers have explored moving the projected area of the DMD in the headlamp FOV to support applications beyond high-resolution ADB headlamps.

Headlamp FOV Matrix and DMD

In standard vehicles without an ADB system, the low-beam and high-beam areas are separated by two modules. The FOV of a standard high beam module is 40 degrees by 10 degrees per headlamp. The modules are aligned to cover a total of 80 degrees by 10 degrees of the vehicle's high-beam FOV. A basic ADB system uses a limited number of pixels (typically 12 pixels per headlight, 24 pixels total) to control the entire 80-degree by 10-degree high-beam space. Typically, these ADB systems have no controls in the vertical area, meaning that one partition covers the full 10 degrees vertically. As resolution increases, the ADB system utilizes a 2D pixel matrix to achieve high beam zoning, thereby providing vertical control and maximizing the amount of light projected onto the road. Figure 2 shows an example ADB system with only 12 zones per headlamp and no high beam vertical control function since only a 1D matrix is shown. Areas above and below oncoming vehicles and areas surrounded by DLP® around traffic signs can actually be illuminated with higher-resolution light, allowing the driver to see objects or oncoming obstacles.

OEMs and Tier 1 headlamp suppliers are already looking for ways to provide higher resolution for ADB systems, especially in the center of the high-beam FOV. Since road hazards are often directly in front of the vehicle, the center of the high-beam FOV is critical to maximize the amount of light. Current automotive headlight high-beam module illumination distribution usually has a smaller peak brightness area near the center.

Figure 3 shows a standard high beam illuminance distribution, the idea being that high resolution is only required in the center of the high beam FOV. Achieving high resolution near the edge of the high-beam FOV exponentially increases system complexity and cost without providing commensurate functional gains. Therefore, Tier 1 headlamp suppliers designed new headlamps with a third module that provides high resolution only in the center of the vehicle's FOV. DLP automotive technology enables a cost-effective, high-resolution area that directly addresses this new headlight architecture while enabling Tier 1 headlight suppliers to easily create modular designs and support multiple vehicle trims.

Figure 3. Typical high-beam illuminance distribution with high central peak.

The DLP5533A-Q1 DMD is optimized to support modules covering a 14-degree by 7-degree FOV; each headlight typically uses one of these modules. But two DLP5533A-Q1 modules (one for each headlight) can generate a high-resolution area of 28 degrees by 7 degrees for the vehicle's FOV.

Figure 4 shows the example headlight FOV segmentation with high-resolution areas from Figure 2,

Figure 4. DLP headlight FOV breakdown.

In Figure 4, a high-resolution area of 28 degrees by 7 degrees was placed to cover the space in the low- and high-beam FOV. In addition to providing ADB support (high-resolution area in the high-beam FOV), this crossover capability also enables DLP headlight modules to project high-resolution symbols on loads in the "HR graphics area" of the low-beam FOV. .

The DLP5533A-Q1 is ideally suited for symbol projection because it provides the resolution needed to create understandable symbols, such as a right-turn arrow that indicates a driver needs to turn right. Due to the orientation of vehicle headlights, the relationship between resolution and clarity of symbols projected by the headlights is more pronounced than with standard projection displays. Because the headlights do not project on a surface perpendicular to the projection source, the projected symbols can easily become elongated, making them unintelligible to the driver without sufficient angular resolution.

Figure 5 shows the angular resolution of 0.05 degrees per pixel, which can be achieved with a 20,000-pixel matrix dedicated to symbol projection, versus the angular resolution of 0.01 degrees per pixel, which can be achieved with the low-beam area of the DLP5533A-Q1 high-resolution headlight module. ). These angular resolutions correspond to approximately 12 lines and 49 lines respectively when projecting a 2m high image from a distance of 10m.