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ToF: More than just distance measurements

Projects in the field of Industry 4.0 and smart devices place a wide range of demands on modern sensor technology: precise distance measurement, compact design, low power consumption and digital evaluation – time-of-flight (ToF) sensors are ideal for meeting these requirements.

Whether in catering, consumer goods or building automation, ToF sensors enable new applications and simplify existing concepts.

Principle of time of flight illustrated.

Time-of-flight – the principle

A ToF sensor measures distances based on the time it takes for a light signal to travel from the sensor to the object and back. This method enables contactless, fast and reliable measurements in the millimetre range. Unlike classic infrared or ultrasonic sensors, ToF sensors deliver more precise and stable results in many applications – even on surfaces with poor reflectivity. Through the use of filter mechanisms and calibration strategies, modern ToF sensors are able to minimise interference from strong external light sources (e.g. direct sunlight) and highly reflective or absorbent surfaces, while still performing precise distance measurements.

Typical application scenarios

• Industry: Level detection, object detection on conveyor belts
• Smart home: presence detection, automatic lighting control
• Consumer goods: Distance sensor in vacuum cleaners, smartphones or household appliances

Advanced application scenarios

But creative applications can also be easily implemented with ToF sensors:


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Cup & Fill Detection:
ToF sensors with multi-zone measurement enable the simultaneous detection of containers (e.g. cups, mugs or glasses) and their fill level. This allows the position, volume and presence to be determined precisely – for example, for automatic filling machines or smart beverage dispensers.

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Person recognition:
People can be recognised and tracked over long distances – even several people at the same time.

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Intelligent door opening:
The sensor distinguishes between someone walking past the door and someone actually wanting to enter, thus avoiding unnecessary door openings.

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Smart sanitary solutions:
A ToF sensor can be used to implement intelligent controls – for example, to detect people, activate automatic flushing or provide individual welcome effects.

Hardware integration and software control

Modern ToF sensors can usually be connected via I²C or UART. Software integration is carried out via API functions or AT commands, depending on the platform. Sensor values can be transmitted periodically or event-based (e.g. when a threshold value is exceeded).

Many sensors also have an interrupt output – ideal for low-power designs where the main system should only be woken up when needed.

Smart features and expandability

In addition to pure distance measurement, modern ToF modules offer a wide range of additional functions:

• ROI (region of interest) for targeted area measurements

• Autonomous threshold comparison with alarm function

• Multi-zone measurement for simple 1D depth images

• Ambient light cancellation for reliable operation even in the presence of extraneous light

ToF compared to alternatives

Other sensor technologies such as ultrasound or simple IR sensors often reach their limits in terms of resolution, speed and susceptibility to interference. ToF sensors offer a balanced combination of precision, response speed and energy efficiency – and all this with minimal space requirements.

Employee profile Tim Müller

"In my opinion, the ToF sensor will continue to open up new opportunities in the future and find applications in many industries thanks to its versatility and potential for creative ideas."

Tim Müller, Electronics and Firmware Developer at STEINEL Solutions AG