text.skipToContent text.skipToNavigation

Technology of Laser Sensors for Distance Measurement

Laser distance sensors measure positions and distances contactlessly with laser light. They are precise and can be used over long distances, as well as in close range. These sensors are ideal for precise position and distance measurement or for detecting objects regardless of color and surface.

How Do Laser Distance Sensors Work?

Laser sensors are photoelectronic sensors and, thanks to their contactless measuring principle and high accuracy, are well-suited to object detection, path, position and distance measurement. wenglor laser distance sensors work according to the transit time measurement principle and use laser triangulation. In both procedures, distances are measured with laser light and output as a distance value.


When to Use a Triangulation Sensor and When to Use a Transit Time Sensor

Triangulation Sensors for Short Distances

Precise determination of distances in the close range up to 1 m
Detection of very small objects or differences in distance
Linearity deviation < 1 mm
Very fast measurements 
Measurement on different shapes and surfaces
High precision down to the micron range

Transit Time Sensors for Long Distances

Determination of long distances up to 100 m with reflectors
Working range up to 10 m on objects
Linearity deviation > 10 mm
Resistant to interfering influences
Very high ambient light resistance
Reproducible measurement over long distances

Possible Uses of Laser Sensors for Distance Measurement

Presence check

Presence check icon

Thickness measurement

Thickness measurement icon

Diameter control

Diameter control icon

Edge counting

Edge counting icon


Positioning icon

Robot positioning

Robot positioning icon

Stacking height monitoring

Stacking height monitoring icon

Parts measurement

Parts measurement icon

Differential Measurement

Contrast Recognition

Monitoring of Two-Layer Materials

Sectors and Industries which Use Laser Distance Sensors

Triangulation Sensors

Transit Time Sensors

In logistics centers, shuttle systems must automatically deliver goods from the warehouse to production. Time of flight laser distance sensors with wintec integrated on the front detect in advance end positions or forward-moving shuttles in the field of vision up to ten meters ahead so that shuttles can slow down or stop.

In the beverages industry, individual bottles and bottle containers must be placed in Pick-and-Place applications with gripper arms during the automated filling and packaging process.

In the production of hard cheese, it is important to ensure that the blocks of cheese are placed exactly on the conveyor belt. Time-of-flight laser distance sensors with wintec are able to detect the cheese blocks in a fresh, still shiny condition regardless of the positioned angle.

When filling and sealing transparent food trays, their position and presence on a multi-lane conveyor must be reliably recorded. 

In the steel industry, red-hot tubes are transported for cooling on conveyor lines after being manufactured in casting furnaces. In order to control this process, the presence of hot blanks between 700 and 1,000 °C must be reliably detected. 

After production, fired and coated clay tiles are temporarily stored in magazines for cooling and drying. They are then removed and fed to quality control before the packaging plant. 

The Triangulation Principle

The triangulation principle is a geometric measurement method that uses the triangular relationship. In this method, a light point is projected onto the object to be measured. The object reflects the light and hits a light-sensitive CMOS receiving element in the sensor at a certain angle. The position of the light spot on the CMOS line changes depending on the distance of the object. In this way, the distance to the object to be measured can be precisely determined even at small distances. 

This technology enables distance sensors to detect very small details. The triangulation principle is used by the distance sensors CP, OCP, YP, P3 series and PNBC

Do Triangulation Sensors Have a Blind Spot?

Sensors that operate according to the triangulation principle have a so-called blind spot. This is dependent on the distance from which the reflected light meets the receiving element (CMOS line). If the reflected light does not hit the CMOS line, no measurement can be taken. The blind spot is below the working range and means that objects located in this area are not detected and no measured values are output

Example CP24MHT80 laser distance sensor triangulation: 
Working range: 40…160 mm
Blind apot: 0…40 mm

The CMOS Receiving Line

The CMOS line is a light-sensitive receiving element with a large number of pixels. It is used to evaluate the position at which the laser light hits the line. The electrical charge in the pixels of the CMOS sensors (Complementary Metal-Oxide Semiconductor) is converted into a voltage. The position of the object can be determined based on the light distribution on the CMOS line. 

The CMOS line enables highly accurate distance measurement and is typically used in laser distance sensors based on the triangulation principle.

Use of Red and Blue Lasers

wenglor’s laser triangulation sensors work with red or blue laser light. Whether red or blue light is used depends on the application. Red laser light has a wavelength of 650 nm. Blue lasers work with a wavelength of 405 nm and therefore have a shorter wavelength. This means that the blue laser beam penetrates less deeply into the object to be measured and delivers precise and stable results. Glowing surfaces in particular are not affected by the blue laser. Laser distance sensors with blue diode are very well suited for organic surfaces, polished metals, shiny plastic surfaces or dark paints.


How to Install Triangulation Sensors Properly

To achieve the most stable object detection and measurement possible, the following instructions must be observed when adjusting the sensor.

Round, Glossy, Reflective Objects

When measuring shiny or round surfaces, it should be ensured during sensor installation that no direct reflections fall on the receiving element.

Tip: Align the sensor so that it is positioned in an axis with the round object. 

Steps, Edges, Recesses

For all distance sensors, it should be ensured that the receiving beam has a direct line of sight and is not covered by an obstacle such as an edge, step, hole or gap.

Tip: Align the sensor orthogonally to the gap course!

Moving Objects

One example of moving objects to be measured is conveyor belts. It is important that the object moves orthogonally to the sensor. This prevents direct reflections to the receiver.

Tip: Install the sensor orthogonally!

Color Edges

When measuring objects with color transitions, so-called color edges, it is important that the color edge runs orthogonally to the sensor. This prevents color errors.

Tip: Install the sensor orthogonally!

Differences Between Spherical and Aspherical Lenses

Spherical Lens

  • The lens has a spherical surface

  • Incoming light on the edge area is more strongly refracted than in the central area

  • Bundling of the light beams leads to a loss of precision 

Aspheric Lens

  • The lens has an uneven curvature

  • The light beam is evenly broken over the entire surface

  • Lens shape reduces imaging errors

  • Focus point is mapped precisely on the line

  • Very high measuring accuracy

Time of Flight Principle (ToF)

The ToF (Time-of-Flight) laser sensors for distance measurement combine reproducible measurement results, reliability and a large measuring range. This makes them suitable for a variety of applications at distances of up to one hundred meters with reflectors or ten meters to objects. 

The Time-of-Flight measuring principle, also known as transit time measurement, calculates the distance L to the object via light pulses. The diode in the sensor emits laser pulses that are reflected by the object. The time interval from the emission of the light pulse to the object and back again is measured. The time T and the light speed C then provide the corresponding distance to the object

The following physical formula is used to determine the distance:
L = ½ × C × T 

The Time-of-Flight measuring principle is used by the distance sensors P1PY, P2PY, P1KY and OY

The Most Important Facts About the Speed of Light at a Glance

The speed of light is a fundamental constant of physics. In vacuum, it is 299,792,458 m/s. Nothing moves as fast as light.

Do ToF Sensors Have a Blind Spot?

ToF sensors have no blind spot. Objects can be detected below the setting range and the sensor switches, but cannot provide any measurement results.

Output of Distance Values

Digital Switching Output

Distances can be taught in via digital switching outputs. As soon as the taught-in distance is reached, the sensor outputs a switching signal at the output. This enables objects to be detected and positions to be detected.

Analog Output

The distance value is output as a linearly proportional current (4…20 mA) or voltage value (0…10 V) via an analog output. The characteristic curve can be set within the entire measuring range by teaching in. 


IO-Link technology is used around the world for standardized communication with sensors and actuators. This is point-to-point communication.

Industrial Ethernet

Industrial Ethernet is a generic term for all Ethernet standards for real-time data transmission between the control and sensor. Industrial Ethernet protocols include, for example, EtherCAT, Ethernet/IP or PROFINET.

What Is Accuracy?

High accuracy means that the anticipated measurement results are achieved. This term is only used for qualitative statements. This means that it is not a technical parameter. Accuracy is made up of precision and correctness. The accuracy always depends on the measuring principle used.


Precision, also known as repetition accuracy, can be determined by successive measurements under consistent conditions. A very precise value therefore delivers almost constant measurements. The precision of a sensor is quantified by reproducibility.


Correctness is a qualitative value. It is defined by linearity deviation, temperature drift, switch-on drift and switching distance deviation.

The figure shows how correctness, precision and accuracy are related. The red dots represent successive measurements from a sensor, while the target indicates the correct value. If the measured values are far apart and far away from the target, this indicates a low precision and correctness. Ideally, measurements should be correct and accurate, meaning they are close together and within the target range.

Starting point
A distance measurement is carried out and the maximum possible deviation is determined. It is always measured on the same object to rule out color errors. The ambient temperature may vary by 10 °C.

Values from the data sheet: 

  • Reproducibility: 3 mm
  • Linearity deviation: 10 mm
  • Temperature drift:  0.4 mm/K

Precision (reproducibility) + correctness (linearity deviation, temperature drift) = accuracy 
mm + 10 mm + (0.4 mm * 10 °C) = 17 mm

What Determines the Accuracy of the Measurement Results?

Time-of-flight laser distance sensors achieve high measuring ranges of up to 10 m on objects and 100 m on reflectors. Triangulation laser distance sensors, on the other hand, is very accurate. However, the measuring range is restricted to max. 1,000 mm. Various settings can be made to optimize the accuracy of the sensors for distance measurement depending on the application. This means that the accuracy can be further increased by filter functions.

Laser Classes and Their Modes of Action

What Is the Difference Between Normal Light and Laser Light?

Normal Light

Dispersion directionLight waves are dispersed in all directions
WavelengthsConsist of many different wavelengths
Phase equivalenceWaves oscillate out of phase
Divergent light beam with large spot diameter

Laser Light

Light waves are strongly directed
Consists of one wavelength (monochromaticity)
Waves oscillate synchronously
-> Strong bundling enables small light spot diameters at great distances.

Why Is There Red and Blue Laser Light?

The light spectrum consists of different wavelengths. Each has a different color. A color can be assigned to each wave in the color spectrum. Red light differs from blue light in its wavelength and energy density.
Wavelength blue: 380 – 500 nm
Wavelength red: 640 – 675 nm

What Is Light?

Light is the part of electromagnetic radiation visible to the human eye. The radiation propagates in different wavelength ranges when emitted by a light source, for example a light bulb. The wavelength range lies between UV radiation (shorter wavelengths) and infrared radiation (longer wavelengths).

What Is Color?

The color of objects is a subjective impression created by objects absorbing different wavelengths and reflecting others. These wavelengths represent different colors. The color reflected by the object can be perceived by the human eye. 

What Is a Laser?

The term laser stands for Light Amplification by Stimulated Emission of Radiation. A laser beam can be generated over a wide range of the optical spectrum. In simple terms, this means that directed light waves are bundled into a beam in high concentration.

Differences Between Laser Distance Sensors and Ultrasonic Sensors

  • Distance sensors and ultrasonic sensors differ in the size of the detection range

  • Ultrasonic sensors work with a wide sonic cone 

  • Laser distance sensors work with a fine laser beam

Product Comparison