Sensor with flicker detect boosts camera performance in IoT devices

By simultaneously providing scene colour temperature, ultra-violet (UVA) radiation level, and lighting frequency information, the VD6281 lets the camera correct white balance and enhance colour presentation, and sets appropriate exposure times for the camera to avoid flicker artefacts and eliminate banding in pictures and videos, especially in scenes lit with contemporary LED sources.

"Leveraging the Company's extensive camera system know-how, ST's new VD6281 offers customers a state-of-the-art multispectral ambient light sensor," said Eric Aussedat, General Manager of ST's Imaging Division.

"Our roadmap for ALS and flicker sensors is an ideal complement to ST's market-leading FlightSense Time-of-Flight (ToF) product portfolio. With a growing number of high quality, high resolution cameras per phone, our goal is to offer an advanced solution to assist white-balance correction and remove flicker artefacts in smartphone camera images. Mobiles equipped with VD6281 were already released in 2018, and many others will be coming soon."

With its small form factor of 1.83x1.0x0.55mm, the VD6281 is the smallest multispectral ambient light sensor available, allowing integration in bezel-free smartphones with small notches and inside smartwatches, where a high screen ratio is at a premium.

The sensor uses high performance, direct-deposition filter material to create six independent colour channels: Red, Green, Blue, near-Infrared, UVA and Clear for colour-sensing capability and CCT (Colour-Correlated Temperature) over a wide field-of-view of 120°, enabling accurate assistance for white-balance algorithms, even in difficult conditions including low contrast scenes, low light levels, or exotic artificial lighting.

The VD6281 is in production and available now from ST sales channels.

ST has created innovative photodiode structures and a patented analog readout to boost sensitivity and reduce system noise while maintaining a tiny die area. The VD6281 is up to five times more sensitive than other colour sensors in the market, allowing integration behind a coverglass, inside an optical module with another companion chip or flashLED, or through an opaque phone back cover, supporting optimal industrial design.

With sensitivity and noise control, concurrent UVA, RGB and IR sensing is now a reality. Extracted UVA information can help the camera system determine whether the user is indoors or outdoors and assist the image colour rendering under artificial or natural light. The VD6281 can detect light levels as low as 1mLux, works in less than 8ms (1 video frame at 120fps), and consumes less than 1mW in the ALS mode.

The VD6281 also embeds a patented flicker engine to detect fast artificial light variations. The sensor can detect all lighting frequencies from 50Hz to 2kHz with better than three percent accuracy, including PWM square signals generated by LED emissions. The VD6281 can output flicker information in both analogue and digital format in parallel with ALS operation.

In conjunction with algorithms and host-processing, it is able to detect multiple light frequency harmonics in a scene to capture pictures or video clips without the 'banding effect' even in scenes with a complex mix of conventional lighting sources, including tungsten, halogen, neon, fluorescent, and LED.

ST's VD6281 module is simple to use (6 pins), is I2C based, and comes with a turnkey software driver compatible with Android platforms for fast and simple integration. The module package is reflowable, Lead-Free and RoHS compliant.