Colour sensor for mobiles aids accuracy, adds new light source detection

February 09, 2015 // By Graham Prophet
ams’ TCS3490 intelligent colour sensor’s accurate measurement of colour temperature and ambient light intensity enables sophisticated display colour management control for smartphones, tablets, notebooks and digital still cameras

The sensor is intended to optimise light source detection when operating under a wide range of light sources. Providing accurate colour and light intensity measurements, the TCS3490 enables designers of portable devices such as smartphones and tablets to implement more sophisticated display management and brightness control.

This integrated five-channel colour sensor has extremely accurate measurements of the Correlated Colour Temperature (CCT) of light. As sensors continue to proliferate in today’s mobile electronics market, manufacturers of mobile devices such as smartphones, tablets and laptops can use these measurements to dynamically adapt the display’s colour palette to improve the viewing experience.

In addition to the traditional red, green and blue (RGB) colour sensor channels, included is a dedicated infra-red (IR) measurement channel for the reliable detection of the IR signature of ambient light sources. This enables stand-alone cameras and smartphones to adjust the colour temperature of the flash to produce better photographs in both indoor and outdoor environments. Colour measurements are affected by changes in the IR content of the light, so a passband clear (C) channel photo-diode is included to provide a direct measurement reference for mathematically subtracting unwanted residual IR energy. An integrated IR blocking filter over the RGBC photo-diodes minimises IR spectral component effects, and this also helps to improve colour accuracy measurements.

The fifth IR channel is sensitive to IR light in the spectrum 700nm – 1,100nm. Since every light source has its own spectral fingerprint, with known proportions of ultra-violet (UV), RGB and IR light, a system can identify the light source in the user’s vicinity by measuring the IR-to-C and Red-to-C channel ratios and applying a detection algorithm to the measurements. In smartphone camera applications and digital still cameras, this ability to reliably detect the light source enables the white-balancing settings in a camera’s or smartphone’s flash to be optimised, resulting in improved picture quality.

By measuring the CCT and brightness (lux) of ambient light in a system, consumer electronics devices can automatically adjust the colour tones of the display for the best viewing experience under varying lighting conditions and behind attenuating dark inked glass or spectrally distorting materials. By adjusting the display’s colour tones and hues, the device can make images appear more vivid, more natural or more calm under any changing lighting conditions.

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