A smartphone user frames a shot of their cat crouched in the hallway shadows. Pulses of light travel from the device, bounce off the cat, and return — allowing the phone’s direct time-of-flight (dToF) sensor to precisely measure distance. The phone automatically sharpens its focus, producing a crisp, clear image. This seamless experience, taken for granted by millions of users, is the result of finely tuned optical sensing technology working behind the scenes.
extremely short, we’re talking a few hundred picoseconds.) When this light hits an object and reflects back, the sensor detects it using an array of single photon avalanche diodes (SPADs), which are highly sensitive to even the faintest returning photons. The sensor’s time-to-digital converter (TDC) acts as a stopwatch, measuring the time taken from pulse emission to the received signal. Since the speed of light is a known constant, the distance to the object can be calculated using the formula:
A single pulse isn’t enough to ensure accuracy, so the sensor fires off hundreds of thousands of pulses per measurement cycle. The results are compiled into a histogram and processed by an embedded microcontroller, which determines the distance along with a confidence score based on the signal-to-noise ratio (SNR). This data is transmitted via a simple I²C interface.
But dToF isn’t just advancing smartphone photography. This same technology is making its
Photo Travel Time
Measured Distance =
x Speed of Light
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way into industrial automation and consumer electronics, where devices are increasingly relying on spatial awareness to trigger functions or adapt intelligently to user behavior. Whether it’s a robot vacuum effortlessly dodging furniture and curious pets, or a facial recognition system that wakes up when someone approaches — dToF sensors are enabling intuitive interactions within a broad spectrum of environments. In this article, we will explore the fundamentals of dToF sensing, and how the TMF8806 sensor from ams OSRAM is enhancing ranging solutions.
How dToF sensors work
A dToF sensor operates by emitting an extremely short pulse of infrared light using a vertical cavity surface emitting laser (VCSEL). (By
we get technical
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