New Sensor Claims an “Industry First” for Detecting Harmful UV-A Radiation

October 14, 2021 by Kristijan Nelkovski

Built for wearable devices, the new UV-detection chip can help users monitor their exposure to the most harmful type of radiation: UV-A.

One of the key drivers to advance wearable technology is sensors. New sensing chips allow mobile devices to ship out of the box with highly advanced abilities—from pinpointing a user's exact location to measuring heart rate and blood oxygen levels.

Last week, ams OSRAM released a new ambient UV-detection chip called TSL2585, which, according to the company, is the first sensor of its class and size that can detect UV-A-type radiation. The company hopes this sensor will allow wearable users to monitor their exposure to some of the sun’s more dangerous rays. 



The TSL2585 sensor. Image used courtesy of ams OSRAM

The Danger of UV-A Radiation

Out of the three types of UV light that radiate from the sun—UV-A, UV-B, and UV-C—UV-A is the most harmful to the human body because its wavelength, the longest of the three, has the highest penetrative power. 

UV-A radiation accounts for about ninety percent of all of the UV light that reaches the Earth’s surface. The other ten percent are UV-B rays. UV-C rays are blocked by Earth's atmosphere and never reach the surface of the planet.


UV-A radiation penetrates lower layers of the human skin

UV-A radiation penetrates lower layers of the human skin. Image used courtesy of the FDA

The wavelength of UV light covers the EM region of 100 nm to 400 nm while the UV-A light falls into the 315 nm to 400 nm band. Even though UV rays aren’t a form of ionizing radiation, they can still be harmful to human health. In particular, UV-A radiation can damage cells, which may lead to skin cancer and other skin disorders, eye problems, and immune system issues.


Highlights of ams OSRAM's UV-A-detecting Sensor

The TSL2585 sensor is an ambient light sensor (ALS) with UV and light flicker detection. The device is a six-pin, OLGA (organic land grid array) package sensor with a 1.8 V I2C interface capable of up to 1Mbit/s transfer speeds in fast mode. Its footprint measures 2 mm x 1 mm x 0.35 mm.


Block diagram of the TSL2585 sensor

Block diagram of the TSL2585 sensor. Image used courtesy of ams OSRAM

Internally, the sensor uses photopic, IR, and UV photodiodes to provide ambient light, UV, and light flicker detection information. ams OSRAM manufactures these sensors with interference filters that cover each individual photodiode pixel to detect photons from the right EM band. The sensor also features three integrated modulators with up to 14 kHz fast sampling rate. 

According to ams OSRAM, the sensor can detect ambient light even if it’s covered by materials with low transmissivity. This enables a TSL2585 chip to provide reliable ALS data when embedded under a device’s screen, such as an OLED display.


How TSL2585 Helps IoT Devices Pick Up on UV-A Rays

ams OSRAM designed the TSL2585 primarily for wearables like smartwatches or smart armbands. Wearables with UV-A detection can monitor a user’s UV radiation exposure, allowing him or her to take the proper preventative precautions, like seeking shelter or using sunscreen.

The same principle can also be applied for smartphones, which are ams OSRAM's second intended application for the TSL2585 sensor. However, ams OSRAM notes that when embedded in smartphone designs, this sensor is not as effective as it would be in a wearable that is constantly exposed to a user's ambient environment.


TSL2585 evaluation kit

ams OSRAM also offers a TSL2585 evaluation kit, which includes the main controller board with a PIC microcontroller, a USB 2.0 interface, a TSL2585 module daughtercard, plug and play USB HID class drivers, and GUI software. Image used courtesy of ams OSRAM

The TSL2585 can also be used as a device’s main ambient light sensor, which commonly regulates display brightness in phones and tablets. It can easily convert the UV-A readouts into a viable ambient UV index estimation. This helps the camera with auto-exposure and flicker detection.

Beyond wearables and smartphones, this sensor module can be used in IoT devices. When integrated into smart homes (or even smart cities), the TSL2585 is said to provide more in-depth data on different levels of UV radiation, measured from multiple stationary locations throughout a day. 


Future Use Cases for UV-A-detecting Sensors

ams OSRAM says the TSL2585 is the first sensor to include UV-A detection. In the future, this technology may expand into other use cases, from distance sensing to particle sensing. For example, UV-A-detecting sensors may someday be used under the screen of mobile cameras. Alternately, they may find use in ultra-small particle detectors—ranging from subatomic particles to dust.


Featured image (modified) used courtesy of Safety Glasses USA and ams OSRAM