Implementing front-facing light and proximity sensing functions on smartphones
Works behind the OLED screen, maximizing screen ratio

ams announced on the 8th that it is launching a new RGB light and IR proximity sensor IC, the 'TCS3701', which can accurately measure the intensity of ambient light behind an OLED screen.
The TCS3701 perfectly fits the industry's latest design trend of eliminating the front bezel where ambient light and proximity sensors are typically located in smartphones.

ams's newly developed "Behind OLED" ambient light and proximity sensor enables a wider screen-to-body ratio by activating key touchscreen inactive areas. Furthermore, RGB/IR sensors enable automatic display brightness and color adjustment.

Despite the limitation of having to operate behind a light-emitting OLED display, the TCS3701 can detect additional ambient light that penetrates the light from the display pixels located on top of the sensor.

ams has developed an algorithm that can measure the exact level of ambient light without information about the brightness of the display pixels.

The light transmittance of an OLED screen is limited by the screen's opacity. However, the TCS3701's ultra-high sensitivity to light enables accurate light measurements even under poor light transmission conditions.

The TCS3701 is available in a 2.0mm x 2.5mm x 0.5mm OQFN package, small enough to fit behind a smartphone OLED screen. This small footprint gives smartphone design engineers the flexibility to mount the IR emitter in the optimal front-facing location for proximity sensing. Furthermore, a crosstalk compensation algorithm is provided to ensure reliable proximity sensing performance.

“Today’s smartphone OEMs are striving to maximize their devices’ screen-to-body ratio by minimizing the bezel area on the display,” said David Moon, Senior Marketing Manager at ams. “The TCS3701 enables handset designers to address this trend, ultimately achieving bezel-free design.”

“The reason this sensor can operate behind an OLED screen is because of the unique ultra-high sensitivity of the device itself,” he added, “and also thanks to a sophisticated measurement algorithm designed to compensate for optical distortion caused by the OLED screen.”

The TCS3701 is currently sampling and priced at $1.25 per unit in quantities of 1,000.