DLP® Dynamic Floor Projection Technology for Automotive Exterior Lighting
Latest update time：2020-09-28
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Introduction
Dynamic floor projection technology, capable of displaying any pattern within the same module, is reshaping consumers’ perception of exterior lighting by offering new and innovative lighting features. Innovative lighting features include automotive light “carpets” that illuminate the surrounding area outside the vehicle or project vehicle information from the side mirrors, such as EV charge level and remaining range, tire pressure warnings, traffic warnings, turn indicators, check engine light warnings, gas level/mileage, etc. Floor lighting also has other enhancements that help the car communicate with the driver and pedestrians, including corner lighting, reverse lighting, vehicle customization and parking indicators.
Dynamic ground lighting systems support high-resolution projection for clearer communication and safer driving. These systems also need to be compact and small enough (about 50mm in length, 25mm in width and height) to be installed in doors, side mirrors, headlights, taillights, or embedded in front and rear bumpers.
DLP® technology can project dynamic content onto the ground or other surfaces around the vehicle, which has many advantages: it not only allows vehicles to communicate with pedestrians, but also conveys more complex information to drivers in a more intuitive way to surrounding vehicles.
A brief history of automotive lighting
In recent decades, many changes have taken place in automotive lighting systems, among which the lighting technology used in rear, side and front lighting has changed greatly. The light source of automotive headlights has evolved from tungsten halogen lamps to high-intensity discharge bulbs to high-power white light LEDs, achieving higher luminous flux and efficiency and extending working life.
Many headlamps utilize an integrated light source configuration that includes a reflective lens and lens system to provide high beam, low beam, and fog light functions. Similar layouts are combined with rear lamps and rear fog lamps to provide multiple signal functions. Other vehicle-mounted lighting includes side mirror lighting for redundant turn signals, night lighting, and center high mounted stop lights (CHMSL). Auxiliary vehicle lighting includes other customized functions such as automaker logo lighting and even projected logo lights located on the interior of the vehicle doors.
Automotive lighting systems must comply with regulations from the National Highway Traffic Safety Administration or the Economic Commission for Europe for standardized signal and reflective components. Headlamp safety requirements are also becoming more stringent, with mandatory beam shape regulations and precision photometry requirements.
Designers must adhere to these requirements while also meeting the practical and cosmetic requirements of manufacturers for the automotive form factor. DLP technology not only easily meets these requirements by supplementing any light source with a digital micromirror device (DMD), a programmable micro-electromechanical system reflective array, but also further enhances the overall functionality of the light beam.
DLP Technology Overview
DLP technology can display dynamic content through the use of DMD. The DMD contains up to 8.3 million micromirrors that can be switched between two positions to redirect incident light based on electrical input (Figure 1). The technology also requires subsequent image processing, memory, light source, and projection optics to control the system and display dynamic content.
Figure 1. DLP technology displays high-resolution images by controlling millions of micromirrors at high speed.
DMD reproduces patterns by individually switching micromirrors, which make up the pixels of the projected content. The following five aspects introduce the important role of DLP technology in automotive lighting systems.
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Reprogrammability
DLP technology can dynamically change content without modifying any of the attached optics. This is especially true when compared to more common static projection technologies such as “gobos” (also known as gobos) commonly used in stage lighting applications. Gobo projectors generate images using a woodcut filter similar to a stencil to create a projected light pattern. This type of projection technology is already used in custom road lighting, but the DLP® Dynamic Ground Projection technology image used in automotive exterior lighting is not modifiable and therefore must include completely separate modules to generate a static image.
DLP technology is fully programmable, allowing multiple images to be projected at different times. For example, custom lighting in the side mirror light sockets can be simultaneously projected with a door open warning sign, or other complex images that update based on user needs and road conditions. For example, when a door is opened or the driver places their hand on the door handle, a warning sign will be projected to warn that the door is about to open. This can be helpful for cars parked near bike lanes.
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Full color gamut support
Static projection techniques are usually limited to displaying images in a single color. For example, Gobo uses a dichroic template to project color images, but dichroic filters can only produce a single color.
DLP technology supports full color by rapidly transmitting red, green and blue LED pulses or laser pulses to the DMD. The DMD switches at a speed of microseconds, so a single imager can be used for all three colors to produce brilliant images and videos.
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Not restricted by light source
Because DLP technology is a reflection-based technology, any type of light source can be used, including LEDs and laser diodes, which will replace incandescent or gas-discharge lamp sources used in front and rear lighting. With this flexibility, DLP technology can accommodate a variety of lighting technologies in various wavelength ranges (including visible light and near-infrared light) in automotive lighting and communication systems.
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Meets automotive grade requirements
Automotive-grade DMDs, DMD controllers, and power management ICs now operate over a –40°C to 105°C temperature range and pass the necessary ESD certification for automotive ICs, enabling the use of DLP technology in today’s automotive lighting systems.
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Compact size
The main goal of automotive lighting systems is to enhance the aesthetic appearance of the car. In addition to the overall shape and material of the car, the lighting system is a key element in creating a sophisticated appearance. There is a lot of work involved in designing the shape of automotive lights, and typically the tolerances of the internal circuits are even tighter. The entire DLP subsystem can be easily installed in the narrow slots in the side mirrors or other small areas around the car.
DLP Technology Use Cases
Given these advantages, DLP technology has a bright future in automotive lighting applications. Below are some possible applications of DLP technology and automotive lighting systems.
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Small car exterior lights
DLP technology can greatly expand the capabilities of automotive exterior lights, including those inside doors, on running boards, or at the base of side mirrors. DLP technology can generate dynamic images without the need for additional moving components. Therefore, exterior lights can be used to project low tire pressure or door open warnings from the side mirrors as the driver approaches the vehicle, or to project vehicle logos or other graphic images and videos from the base of small doors.
These capabilities will allow OEMs to fully customize messaging and branding through small exterior lights, rather than the static logos generated by today’s lights, which can only display a single pattern and cannot be used to communicate with pedestrians or drivers.
Figure 2. Small exterior lights that project a logo onto the ground from the side-view mirror.
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Car Light Carpet
Side mirror lights can perform multiple functions simultaneously, acting as standard turn signals and projecting a blanket of light across the length of the vehicle on the side areas (Figure 3). This type of lighting is particularly useful when the driver is leaving or approaching the vehicle in dimly lit areas or at night.
Figure 3. Automotive light carpet projected from multiple locations on the vehicle.
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Warning to drivers and passengers
DLP technology offers a warning method that is more advanced than the flashing lights and hand gestures that drivers currently use to warn others. Warnings generated using DLP technology can take the form of visual messages displayed on the road surface to indicate information such as hazardous road conditions or special traffic areas such as construction sites or school zones. Drivers can also project a message on the crosswalk or choose to display a preset message on the ground that reads "Safe to Cross" to directly communicate with pedestrians trying to cross the street.
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Broadcast Intent: Private Car
Broadcasting intentions can avoid many accidents caused by nervousness, hesitation or confusion when not knowing where other drivers are moving. DLP projection can communicate simple intentions that are notoriously difficult to articulate, such as a U-turn or a K-turn.
Taxis can use symbol projections to warn oncoming traffic that a vehicle is coming to a complete stop and can project onto the ground to warn that a passenger is about to exit. Vehicles that are exiting a lane and have a blind spot can project their intent to exit. Autonomous functions such as parallel parking or reversing can project their path backwards to indicate their final parking position, clearly communicating their intentions to passing vehicles and cyclists (Figure 4).
Figure 4. Drivers can broadcast their intended trajectory by projecting their route onto the ground behind the vehicle using their rear lights.
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Broadcast Intent: Public Vehicle
A fire truck, ambulance, or police car can broadcast its exact route so drivers of nearby vehicles have a better idea of where to move to yield the right of way. A police car can communicate its intention to ask the driver ahead to pull over or change lanes to pass. Large vehicles that require a large turning radius, such as buses and tractor-trailers, may need to communicate to drivers behind them that they need to back up to make a successful turn. A bus can project its route to and from a public stop so drivers of nearby vehicles have a better idea of its movement. A tractor-trailer carrying an oversized load can project the exact amount of space other vehicles should yield when passing in a tight space. A school bus can also project its intention to keep passengers safe. For example, instead of using a standard stop sign, a school bus could project a stop sign in all lanes.
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Route guidance
The DLP subsystem can assist navigation by augmenting the driver’s field of view with graphics (for example, showing lane lines where none exist). The idea is to build on real-time visual guidance, helping the driver while also announcing to nearby vehicles where the driver is headed next.
in conclusion
Dynamic ground projection is the future of automotive lighting systems and is also the trend for adaptive high beam technology. The ability to individually control millions of pixels in a projection system enables a variety of vehicle applications. Compared to other static projection technologies such as Gobo, DLP technology offers greater flexibility and a small, reprogrammable, multi-color platform with high resolution.
Additionally, DLP technology is leading the pack among dynamic digital projection technologies due to its relative cost-effectiveness, flexibility to accommodate different light sources, and overall efficiency. Given that DLP chipsets are already automotive-grade qualified and feature custom processing specific to automotive applications, their time to market could be shortened. The automotive lighting industry has the potential to benefit greatly by taking advantage of these technology leaps and implementing spatial light modulators such as DMDs for agile beam lighting and message/symbol projection.
Source: Texas Instruments
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