Focus-Induced Photoresponse (FIP)
A novel approach to measure distances

Working principle


Focus-Induced Photoresponse (FIP) is a novel approach to measure distances. Its working principle is fundamentally different from established techniques to acquire depth information, such as time-of-flight, triangulation, or image processing-based methods.

FIP takes advantage of a particular phenomenon in photodetector devices: an irradiance-dependent photoresponse. The photoresponse of these devices depends not only on the amount of light incident, but also on the size of the light spot on the detector. This phenomenon allows to distinguish whether the same amount of light is focused or defocused on the sensor. We call this the “FIP effect” and use it to measure distance.

Distance measurement


The picture illustrates how the FIP effect can be utilized for distance measurements. The photocurrent of the photodetector reaches its maximum when the light is in focus and decreases symmetrically outside the focus. A change of the distance between light source and lens results in such a change of the spot size on the sensor. By analyzing the photoresponse, the distance between light source and lens can be deduced.

FIP sensor systems


See a FIP system in action: Scanning with independent light sources


FIP is very versatile and can be used for various applications in the area of scanning and tracking, such as motion tracking.  

The FIP effect can be observed in various photodetector devices like thin film photovoltaic technologies, lead sulfide photoconductors and more. This enables us to provide depth sensing from the UV to the infrared range.


Get all the technical details in a 5 minute video


Read also our paper „Focus-Induced Photoresponse: a novel optoelectronic distance measurement technique“ where we explain FIP, show graphs, measuring curves, detectors and calibration.



trinamiX has successfully transferred the working principle of FIP to various applications under the brand name XperYenZ™. Which of our sensor systems is the right choice, depends on your sensing task and need. We are happy to discuss your requirements and find the right sensing solution. Get in contact with us.