Laser Distance Sensors: Triangulation vs Time-of-Flight
Optical distance sensors measure gaps without contact using a laser beam. This guide compares the two core principles, triangulation and time-of-flight (ToF), and shows how to choose the right method by range, accuracy and target surface.
View distance sensorsTriangulation or time-of-flight - how do they differ?
Optical distance sensors send a laser beam to the target and evaluate the returning light. With triangulation, the reflected spot lands on a different position of a line sensor (CMOS/PSD) depending on distance; the range follows from the angle of the triangle formed by emitter, object and receiver. With time-of-flight (ToF), the sensor directly measures the time or phase shift the light needs for the round trip.
The geometry gives a simple rule: triangulation is extremely precise at short range up to a few metres but loses resolution quickly as distance grows. Time-of-flight keeps almost constant accuracy across the whole range and therefore reaches tens of metres and beyond.
Which method fits which application?
The choice depends on measuring range, required accuracy and target surface. For quality inspection, thickness and profile measurement in the micron range, triangulation is the only option. For level, collision protection or positioning over ten metres and more, time-of-flight is the right technology.
- Triangulation: thickness, edge and profile measurement, part inspection, short-range positioning.
- Phase ToF: precise distance measurement up to a few metres, e.g. robot positioning and automation.
- Pulse ToF: level in tall silos, crane positioning, collision protection and outdoor use.
- Dark, glossy or transparent surfaces need a stronger receiver or a reflector.
What matters for accuracy, optics and safety?
Beyond the principle, repeatability, linearity, response time and interface decide suitability. Automation needs analogue outputs (4‑20 mA, 0‑10 V) and bus interfaces such as IO-Link; switching tasks are covered by switching outputs with adjustable thresholds.
- Judge repeatability, not just resolution - it defines real process reliability.
- Account for linearity and temperature drift across the range.
- The light spot must be smaller than the smallest target feature.
- Choose protection rating IP65/IP67 or higher for industrial environments.
- IO-Link allows parameter setting and diagnostics without swapping the sensor.
Frequently asked questions
When is triangulation better than time-of-flight?
Whenever high accuracy at short range up to about two metres is needed, such as thickness, profile and edge measurement. Triangulation reaches resolutions down to the micron range there.
How far do laser distance sensors reach?
Time-of-flight sensors measure onto natural surfaces up to around 300 metres depending on reflectance, and further with a reflector. Triangulation sensors typically cover a few millimetres up to around two metres.
Does object colour affect the measurement?
Yes. Dark, glossy or transparent surfaces reflect less light, so range and stability drop. Data sheet figures usually refer to 90 percent remission.
Are laser distance sensors eye-safe?
Sensors of laser class 1 and 2 are eye-safe under normal conditions. From class 3R upwards, protective measures per DIN EN 60825‑1 are required.
Looking for the right distance sensor?
We supply optical distance sensors using triangulation and time-of-flight - from micron profile measurement to long-range sensing with IO-Link.
Precise
Triangulation with resolution down to the micron range.
Long reach
Time-of-flight sensors measure up to around 300 metres.
Standards checked
Laser classes documented to DIN EN 60825-1.
Expert advice
Specialists help select the right measuring principle.