Low-light image quality, power consumption and high operating temperatures remain key challenges facing automotive OEMs today. These will be some of the major discussion topics at AutoSens Europe 2024, taking place this week in Barcelona, Spain.
For low-light image quality, the key challenge is the tradeoff between pixel array resolution and pixel size. The first image sensors developed and offered into the automotive industry about 20 years ago had a 6-µm pixel size and VGA (640 × 480) resolution. Today, 8-MP resolution is the sweet spot for high-end automotive camera systems. To make this boost in resolution possible, the pixel size had to shrink to 2.1 µm. The result is about 8× less light-sensitive area within a pixel to collect photons. Of course, some of this shrink in pixel size has been compensated by better pixel performance, especially by improving the relevant noise figures. But it remains a challenge to resolve some scene-perception corner cases—for example, detecting lost cargo at longer distances in low-light automated-driving (AD) scenarios on highways at night.
Additionally, we understand that power consumption and high-temperature image quality are real pain points for customers today. With the transition to electric mobility, the power consumption of its electronics has an impact on a vehicle’s driving range. However, for image sensors, there are other complications. For one, higher power consumption leads to higher junction temperature of the device, which directly and substantially impacts the image quality because various critical noise sources scale exponentially with temperature. This problem becomes more significant with the trend toward smaller and smaller camera modules, which impairs the heat dissipation behavior. Hence, the mission profile of automotive cameras has shifted to higher temperatures. But the problem is that most image sensors today have not been designed and developed to work well at these higher temperatures, so their overall performance and image quality are severely impacted. This can result in less-than-suitable image quality for advanced driver-assistance systems (ADAS) and AD perception algorithms.
To address these challenges of the automotive camera industry, a new approach to high-dynamic-range (HDR) imaging is required, with new pixel architectures that overcome the inherent performance tradeoffs of the current devices. Ideally, such new HDR architecture must be able to generate a very large signal-range extension from just a single exposure of the pixel.
With some groundbreaking new developments—and together with our wafer foundry partner—Omnivision has made this technology available in automotive-grade quality and with the performance characteristics required in next-generation automotive camera systems.
Using Omnivision’s proprietary TheiaCel technology, the company has developed automotive image sensors designed to address these specific problems and customer pain points. The new image sensors use single-photodiode lateral-overflow integrating-capacitor (LOFIC) technology, replacing previous-generation solutions that used a so-called split-pixel HDR concept. This new pixel with the TheiaCel architecture avoids additional sensitivity loss and active pixel area by generating HDR imaging from a single photodiode with a greatly extended overall signal range. This is especially useful for the downsized pixels of high-resolution sensors.
The automotive camera industry has reached a performance limit with maintaining good low-light image quality, especially for high-resolution image sensors used in new generations of automotive camera systems. In addition, power consumption figures, higher operating temperatures and smaller camera module designs present further challenges for automotive ADAS and AD applications. The industry is looking for new groundbreaking solutions to enable the next big performance leap.
—Mario Heid is VP of marketing for automotive and medical at Omnivision.
RELATED TOPICS: ADAS, AUTOMATED DRIVING, AUTOMOTIVE, CAMERAS, IMAGE SENSORS
