ActLight SA has been included in “Menalto Adv ...

30 Jan 2018



ActLight SA and its proprietary Dynamic PhotoDiode (DPD) has been selected by Menalto Advisor LLC and included, under the cha ...


ActLight SA closes its series B round

11 Dec 2017



ActLight SA recently closed its series B financing round. With a CHF 1.2 million contribution, Investiere was the largest inv ...


A new sensor increases smartwatch battery lif ...

26 Apr 2017



ActLight, in collaboration with EPFL, developed a new generation of the heart-rate monitor sensors for smart watches. Source



  • High performance

    The DPD has high signal to noise ratio with respect to a standard photodiode due to the absence of amplifier.

  • Low cost

    The DPD sensor and its front-end are implemented on the same chip with a standard low cost CMOS technology.

  • Digital output

    The DPD has high output signal, therefore it can be directly connected to digital circuits.

  • Low voltage

    Our sensor does not require any high voltage. The sensor front-end just uses Vdd.

ActLight’s Dynamic Photodiode (DPD) technology offers technological breakthrough in light sensing.

Traditionally, photodiodes operate at constant reverse bias voltage giving photocurrent as output. Typically, this photocurrent is weak and requires further amplification. An amplifier introduces additional noise, which becomes crucial at low light conditions. Instead of using DC bias, the DPD operates at pulsed voltages: the applied voltage is switched from reverse to forward bias. This forward bias induces a large forward current after a time delay, so called triggering time, which depends on the light intensity. This way, we measure the delay time of the large forward current instead of the small photocurrent magnitude.

Due to the large output signal, the DPD does not require any amplifier, and it can be directly connected to digital circuits. Absence of the amplifier and its associated noise provides a great improvement in the device performance. Based on the standard CMOS technology, the DPD and its simple front-end circuits are integrated on the same chip. The absence of complex analog circuits allows to reduce silicon area and provides cost-effective solution.


Heart rate sensors

  • Increased battery life

    Due to better signal to noise performance of the DPD sensor, less light is needed to get a PPG sample. A reduction of about 7 times in LED transmitted energy was measured with respect to a state of the art system.

  • Small size

    Absence of the complex analog front-end and simple counter-based time-to-digital converter (TDC) allows to achieve improved sensor performance and silicon area reduction.

  • Reduced cost

    Smaller silicon area leads to significant cost reduction. Additionally, our DPD sensor and its read-out front-end circuit are implemented on the same substrate in standard 180 nm CMOS technology.

The smartwatch market is booming. According to the International Data Corporation, nearly 50 million smartwatches were sold worldwide in 2016, and this number is expected to grow to 150 million by 2021. Nowadays the heart rate monitor becomes a must-have feature for the smartwatches and fitness bands.

In the heart rate sensor light emitted by LED and reflected from the hand is measured with a photodiode. The reflected signal depends on the blood concentration. With each cardiac cycle the heart pumps blood which change reflection and output signal of the photodiode. The modulation of the photodiode signal gives information about heart rate.

Heart rate monitors using conventional photodiode require signal amplification, and amplifier becomes the main source of noise. ActLight’s Dynamic Photodiode technology provides direct digital output which eliminates the need of the analog amplifier improving system signal to noise ratio. This means that less light is required to obtain the same heart rate signal. ActLight heart-rate monitor built with standard 180 nm CMOS technology requires 7 times less light with respect to the state of the art system to get the same signal quality.

3D camera for mobile applications

  • High performance at low voltage

    The DPD sensor deliver high optical performance and does not require high voltage.

  • Small pixel size

    The DPD sensor array can have a pixel size below 5 um.

  • Reduced cost

    The DPD sensor and its front-end circuit are implemented on the same substrate in standard low cost CMOS technology.

The interest for 3D and range imaging is exponentially increasing due to its exploitation in mobile applications. The most advanced 3D imaging technique is a Time-of-Flight (ToF) method. In this method a depth image is obtained by measuring light propagation time.

The DPD sensor delivers high optical performance which is especially important in the mobile applications where emitted light power is limited. Our dedicated ToF method offers advantages in terms of compact system realization, good performance, and low required computational power.

In current 3D camera sensors, pixel scaling is limited due to complex analog circuits. The DPD's simple digital front-end allows to decrease pixel size below 5 um. Moreover, the DPD and its read-out front-end circuit are implemented on the same substrate in standard low cost CMOS technology, and does not require high voltage for its operation.


  • High performance at low voltage

    The DPD sensor delivers high optical performance and does not require high voltage compared to APDs.

  • High background light immunity

    Sensors based on SPADs fail to operate at high background light. ActLight's DPD sensor has high background light immunity.

  • Reduced cost

    Smaller silicon area leads to significant cost reduction. Additionally, our DPD sensor and its read-out front-end circuit are implemented on the same substrate in standard 180 nm CMOS technology.

LIDAR (Light Detection and Ranging) uses a laser light to obtain a depth image. In most of the LIDAR sensors used for mapping and self-driving vehicles the time between the emission and reception of the light is computed to determine the time of flight (ToF). Knowing the speed of light and delay time for the return wave we can compute the distance to the object that caused the light to bounce back. That value is the range information that is reported by the sensor.

LIDAR systems are designed to detect objects at long distances, so typically the reflected light is extremely weak. Thus, the high performance photodetectors are used in LIDARs. Moreover, the weak reflected light should be often detected on top of a strong background light, which makes the measurement even more challenging. The DPD solution is imminently suitable for LIDAR applications since it combines high performance sensing with immunity to the strong background light.

About us

ActLight SA focuses in the field of CMOS photonics by developing a new type of photodetector. Being a fabless company, ActLight specializes in the Intellectual Property (IP) of this area and provides supporting services like design and technology advice for its customers.

ActLight SA, a start-up company founded in 2011 and based in Lausanne - Switzerland, developed a disruptive technology in the field of optical light sensors. The patented CMOS-based photonics technology allows to substantially improve the efficiency and accuracy of various light sensing applications like Time-Of-Flight (TOF) based distance measuring and gesture control, heart-rate monitoring, 3D/2D cameras and much more. ActLight operates in markets like mobile and wearable devices, healthcare/medtech, autonomous driving,drones and robotics.

Our company, powered by its highly innovative R&D spirit and profiting from collaborations with leading institutions such as the internationally renowned EPFL, has swiftly evolved to become a technology leader in its segment. ActLight SA operates primarily in a licensing business model where revenue is generated from license and royalty fees but also from non-recurring engineering (NRE) projects.

ActLight's team consists of experts in the fields of devices, materials, integration process, characterization techniques, circuits design, marketing and business development. IP protection and sales are performed by top experts located in US, Japan, and Switzerland. Strong advisory board includes both industrial and scientific experts.


Want to know more?

Contact us at

ActLight SA
EPFL Innovation Park, Building I, 1015 Lausanne, Switzerland