Brightness & colour sensor adds flexibility to smartphone display design

February 06, 2015 // By Graham Prophet
Rohm has a colour sensor for display-equipped devices such as smartphones and tablets capable of detecting the colour temperature, brightness, and RGB components of ambient light. Its infrared cutoff function provides greater enclosure design flexibility.

The BH1745NUC uses original infrared removal technology and computing methods to achieve the highest-available infrared cutoff characteristics, reducing the effects of incident infrared rays by over 10-times compared with conventional products. This enables compatibility with dark (low permeability) optical windows – unlike conventional colour sensors that cannot provide accurate detection due to the effects of infrared interference when dark windows are used.

Smartphones, tablets, and other display-equipped devices have begun to integrate colour sensors in order to analyse the RGB components of ambient light for display image adjustment or perform backlight dimming based on the surrounding brightness levels. Conventional colour sensors require a transparent optical window in order to accurately detect visible (i.e. RGB) light. However, the design trend in many smartphones and portable devices is to adopt dark optical windows, which although are more stylish make it difficult to precisely detect colours, since less visible light gets through and the light that does permeate gets mixed in with IR rays.

Rohm has applied optical sensor expertise developed over several years, including original infrared removal technology and proprietary computing methods, to develop a colour sensor that provides unmatched performance – even with dark optical windows. The sensor is capable of filtering only the spectrum of visible light in order to perform more accurate brightness and colour temperature calculations based on ambient conditions.



Supply Voltage Range

2.3 to 3.6 V

Highest Sensitivity

0.005 lx/step

Operating Current Consumption

130 µA (typ.)

Power Down Current Consumption

0.8 µA (typ.)

Operating Temp. Range

-40 to +85C

Rohm Semiconductor;