Optical sensor eliminates flicker for smartphone cameras, says ams
On-chip flicker detection can be reduced in smartphones, via the TCS3408 colour sensor, says ams. Smartphone world-facing cameras with rolling shutter image sensors eliminate unwanted image artefacts – such as banding – that are caused by the flickering of artificial light sources.
LED lighting means that photography increasingly suffers from flicker from the lighting source. The TCS3408 colour sensor measures the colour and brightness of ambient light as well as detecting photometric flicker.
According to ams, the TCS3408 delivers the industry’s highest level of on-chip ambient-light flicker sensitivity, which is three times greater than ams’ earlier sensor, the TCS3707.
David Moon, Senior Product Marketing Manager in the Integrated Optical Sensors business line at ams, said: “Smartphones can now capture vibrant, detailed and artefact-free images in all lighting conditions.”
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 has on-chip flicker detection to provide an accurate measurement of colour and brightness thanks to five concurrent-reading ambient light sensing channels, i.e 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 the 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.
Images can be distorted when visible light modulations from flickering lights are captured while a camera’s rolling shutter is in operation. 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. 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 artefacts and produce images that represent the image seen by the user.
The TCS3408 offers high colour and 10X ambient light sensing (ALS) sensitivity and half the operating power consumption versus competing sensors, claims ams.
The TCS3408 is available now in production volumes.
An evaluation module for the TCS3408 colour sensor is also available.
