Sensors

Sensor eliminates flicker artefacts for smartphone images and videos

29th October 2019
Lanna Deamer

ams has introduced a sensor solution that enables smartphone world-facing cameras with rolling shutter image sensors to eliminate unwanted image artefacts - such as banding - that are caused by the flickering of artificial light sources. With the wide-spread usage of LED lighting, photography increasingly suffers from what is known as flicker from the lighting source.

The higher accuracy and sensitivity of the new TCS3408 colour sensor, which measures the colour and brightness of ambient light as well as detecting photometric flicker, enables a phone’s camera-enhancement imaging system to eliminate flawed artifacts caused by artificial lighting environments.

According to the company, it delivers the industry’s highest level of on-chip ambient-light flicker sensitivity, which is three times greater than the prior generation TCS3707.

David Moon, Senior Product Marketing Manager in the Integrated Optical Sensors business line at ams, said: “The increasing pixel count of today’s high-resolution smartphone cameras enables image capture with extraordinary detail and clarity, however pictures and videos can often be ruined with unsightly banding distortion effects from flickering light sources. Smartphones can now capture vibrant, detailed and artifact-free images in all lighting conditions, thanks to the TCS3408 high sensitivity flicker sensor.” 

Colour sensing for the real world

Mobile phone cameras today typically use basic three-channel Red/Green/Blue (RGB) sensors to approximate colour balancing in the image enhancement system, and have no means of measuring flicker detection. The TCS3408, with on-chip flicker detection, provides an accurate measurement of colour and brightness thanks to five concurrent-reading ambient light sensing channels - a wideband and a clear reference channel in addition to the RGB channels.

The TCS3408 also provides an option to store a sequence of flicker measurements in its internal memory to allow the smartphone’s camera’s video processor to detect higher-order flicker frequencies up to 2kHz. These flicker frequencies are typically found in modern Pulse-Width Modulated (PWM) LED lighting systems now available and becoming increasingly popular in virtually all lighting environments.

How the TCS3408 reduces flicker artifacts

When visible light modulations from flickering lights are captured while a camera’s rolling shutter is in operation, the resulting effect is an image or video with distorted banding artifacts. The TCS3408 device incorporates a flicker detection engine that detects the presence or absence of 50Hz or 60Hz flicker typically generated from incandescent or fluorescent lights.

When flicker is detected, it is captured and reported through internal status registers of the device and the digital I2C interface enables fast reporting of output information with external processing. Knowing that flicker is present, the camera’s video processor synchronises the shutter with the 'on' portion of the relative ambient light output in a scene.

With this additional information from the TCS3408, the video processor can eliminate the distorting banding artifacts and produce images that truly represent the image seen by the user.

ams optical sensing expertise

The TCS3408 is the latest in a line of intelligent optical sensors from ams for use in mobile phones for display colour and brightness management to enhance a cameras image enhancement.

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