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2D/3D Profile Sensor Technology

2D/3D profile sensors measure objects such as weld seams or glue beads, control the precise position of robots, and check roundness or gap dimensions via laser triangulation. The sensors are compatible with the uniVision software and suitable for use with third-party software thanks to their open interfaces.

What Is a 2D/3D Profile Sensor?

wenglor’s 2D/3D profile sensors enable fast and highly precise measurement of contours and surfaces for various areas of application. Profile sensors work according to the principle of laser triangulation, generating detailed 2D height profiles as well as complete 3D point clouds. Thanks to the non-contact measuring process, the sensors are ideally suited for quality assurance, object detection and robot guidance in industrial production.

2D/3D profile sensors are available in two different performance classes:

MLSL: Precise Resolution in a Compact Housing Design

MLWL: Outstanding Product Quality Thanks to High-Quality Optical Components

wenglor offers the right solution for almost every application: from seamless 360-degree measurement to precise weld seam tracking and locating to micrometer-accurate surface inspection. wenglor’s versatile portfolio includes sensors with multiple measuring ranges, different laser powers and various laser wavelengths. 

MLZL 2D/3D Profile Sensor

The MLZL series is ideal for use on welding robots due to its compact format.

2D/3D Profile Sensors Stainless Steel

Profile sensors with stainless steel housings are used in washdown areas that require intensive cleaning.

2D/3D Profile Sensors for Bending Machines

The wenglor portfolio includes preconfigured, plug-and-play 2D/3D profile sensors for use on bending presses.

The Triangulation Principle

Laser triangulation is an optical measuring principle used in 2D/3D profile sensors for high-precision detection of surface profiles as well as intensity evaluation. To do so, a laser projects a fine line onto the surface of the object. The reflected line is detected at a fixed angle, the so-called triangulation angle, by an integrated camera. Since the image chip (also known as the image sensor) consists of many individual pixels, the laser line appears there as a series of individual image points. Each of these points corresponds to a precise position of the laser line in the image chip.

Creating a 2D Height Profile

A 2D/3D profile sensor generates a 2D height profile, also known as a cross-sectional profile, for each measurement. This consists of numerous measuring points arranged next to each other in a line perpendicular to the object’s direction of movement. Each of these points describes the exact distance between the sensor and object surface along the x- and z-axis. Each height value also includes an intensity value. This value provides information on the strength of light reflection and the material or surface properties, e.g., for changing colors, contrasts, degrees of gloss or transparent materials.

Do 2D/3D Profile Sensors Have a Blind Spot?

Yes, 2D/3D profile sensors have a blind spot. This is generally the case for all sensors that work according to the triangulation principle. The blind spot is the area between the sensor’s reference point and the beginning of its measuring range. The decisive factor here is the distance from which the reflected light is mapped to the receiving element (image chip). This is because a measurement can only be taken when the reflected light hits the image chip. Objects that are below the measuring range are not detected and no measured values are output.
Laser outlet
Blind spot
Measuring range
Blind spot
The quality of a 2D height profile depends on the interaction between the laser, camera and analysis module. The height profile represents the real object geometry only when the laser line is projected precisely, the camera focuses it precisely, and the analysis module interprets it reliably – even on complex or demanding surfaces.

From 2D Height Profile to 3D Point Cloud

If the object moves relative to the sensor, for example on a conveyor belt or through a robot guide or actuator, many individual 2D height profiles are created continuously. These are lined up to create a complete three-dimensional representation of the entire object geometry. The 3D point cloud contains the spatial x-, y- and z-coordinates and the corresponding intensity values.

Coordinate System of a 2D/3D Profile Sensor

A clear, defined coordinate system is essential for correctly interpreting and further processing the measurement data captured with a 2D/3D profile sensor. It serves as a spatial reference for all recorded data and enables the sensor to be precisely integrated into higher-level systems such as robot or axis systems. Defining the axis facilitates precise alignment, adjustment and calibration of the sensor in three-dimensional space and ensures that the recorded measurement data is correctly assigned and processed.

The coordinate system of the sensor is matched to its field of view. The zero point lies directly on the laser outlet outside the housing. As a result, the measured values correspond exactly to the real position of the detected object.

Axes at a Glance

x-Axis (Width)

The x-axis runs horizontally along the laser line and defines the width of the captured profile. The associated a-axis describes the rotation around the x-axis, i.e., the sensor’s forward or backward tilt.

y-Axis (Feed Direction)

The y-axis runs in the direction of movement of the object or sensor, typically along a conveyor belt or during scanning. The b-axis represents the rotation around the y-axis and indicates the lateral tilt of the sensor to the left or right.

z-Axis (Height/Distance)

The z-axis points down from the sensor perpendicular to the object and represents the height or the distance between the sensor and surface. The c-axis represents the rotation around the z-axis, i.e., the lateral rotation of the sensor.

Correct Alignment of the 2D/3D Profile Sensor

To achieve exact measurement results, the laser line must be aligned as perpendicularly as possible to the measurement surface. An angle of 90 degrees between the sensor and object surface yields the best results. In this position, the laser light hits the object optimally and the reflected line can be uniformly captured by the camera.

Correct Alignment

Sensor Tilt

The surface’s reflective properties play a key role.

  • A direct, directed reflection occurs on smooth or shiny materials such as metal, glass or coated surfaces. Here, the light is reflected in a similar way to a mirror. In such cases, slightly tilting the sensor can be helpful to deflect reflections from the camera’s visual field and avoid overexposure of the camera chip. Precise adjustment of the angle is crucial.

  • Diffuse reflection occurs on matte, rough or structured surfaces. The light is scattered evenly in many directions, which usually results in more stable signal detection. However, inaccurate alignment and diffuse materials can affect the intensity distribution or measuring accuracy.

For a uniform signal distribution and optimal profile quality, tilting should be avoided if possible. Thanks to their large dynamic range, 2D/3D profile sensors continue to provide reliable measured values even with a slight tilt.

The following applies in general: Even small deviations from the ideal angle can have a positive or negative effect on the signal quality and profile data, depending on the surface properties. Deliberate, application-specific alignment of the sensor is therefore crucial: Vertical where this gives stability, and specifically tilted where reflections are to be avoided or controlled.

Shadowing

Shadowing means that the field of view is completely or partially covered by the object or adjacent structures. As a result, certain areas of the projected laser line are no longer captured by the camera, resulting in incomplete profiles. Shadowing often occurs on edges, steep steps or deep indentations in the object. Even with complex component geometries or significant height differences, shadowing makes the complete detection and evaluation of the object surface more difficult.

How to Prevent Shadowing?

Shadows can be avoided by specifically adjusting the object within the sensor’s measuring range.
 

Avoiding Shadows from Edges, Steep Steps and Recesses

If an object is positioned so that edges, steep steps or vertical surfaces protrude directly into the sensor’s field of view, these areas can block other features that could be inspected. A slight rotation or tilting of the object ensures that all relevant surfaces for the sensor remain visible and no important measurement data is obscured.

Components with deep indentations can also cause shadowing of the characteristics to be inspected in the rear of the object. Therefore, when placing the object, make sure that all important surfaces are in the sensor’s field of view.

Shadows do not represent a measurement error, but a geometrical restriction. A good sensor setup minimizes these constraints and ensures that the entire contour of an object is detected reliably and completely.

Main Components of a 2D/3D Profile Sensor at a Glance

Laser module
Analysis module
Integrated camera
The laser module is one of the three most important main components of a 2D/3D profile sensor. It creates a high-precision laser line that is used to capture detailed surface profiles as well as perform height measurements. This is done by extending the laser dot into a line through a series of optical elements. With the help of this precise laser line, the object can be scanned with very high accuracy while even the smallest height differences and surface structures can be detected.
Unlike conventional image processing systems, 2D/3D profile sensors do not require additional illumination. The laser produces a precise laser line with particularly high intensity. As a result, laser triangulation remains stable even in strong ambient light and delivers precise measurement results. Since the laser module is fully integrated into the sensor and mechanically fixed, time-consuming adjustments are unnecessary and there is no potential interference from external light sources.

The performance of the laser module is largely determined by the laser wavelength and laser class.

Laser Wavelength

Lasers with different wavelengths are used depending on the application. This makes it possible to adjust optimally to different surfaces, materials or ambient conditions.

Laser Class

The sensors are available in different laser classes. These indicate the power of the laser and determine how intensely the light is emitted.

Another important component of 2D/3D profile sensors is their integrated camera. It captures the reflected laser line with the highest precision. The camera consists of a high-quality lens and a powerful camera chip that captures light information with pixel accuracy and converts it into digital measurement data. The resolution of the camera, i.e., the number of pixels per profile line, determines the level of detail. The higher the resolution, the finer are the contours, edges and surface features that can be represented.

Factory calibration and mechanical fixing of the camera unit ensure consistent measurement stability while eliminating costly adjustments. The interaction between the laser optics and camera technology thus enables each individual profile point to be precisely determined in three-dimensional space, thus creating a reliable basis for reproducible measurement results.

The analysis module serves as the computing center of the 2D/3D profile sensor. Here, the raw data recorded by the camera is converted into digital measurement data. Due to the interplay of image acquisition, evaluation and interface communication, it is crucial for the performance of in-line measurement systems.

For maximum flexibility, 2D/3D profile sensors have two selectable operating modes designed to meet different requirements, meaning they can be used in any number of applications. Both operating modes access the same powerful hardware platform. Thanks to integrated processors and stable computing architecture, high profile rates and large amounts of data can also be processed and sent reliably.

Mode of Operation: Smart Profile Sensor

Mode of Operation: Profile Generator

In “Smart Profile Sensor” mode, the entire profile is evaluated directly on the sensor, no additional hardware is required. The profile information collected is analyzed using configurable algorithms. The result is a signal that has already been interpreted and evaluated, such as a distance value, an edge position or a good/bad signal. This prepared profile data can be sent directly to a controller or robot without additional processing and enables seamless integration into existing processes.
In “Profile generator” mode, 2D/3D profile sensors provide a complete two-dimensional height profile. The raw measurement data is sent as a point cloud or profile data stream and processed further by a higher-level analysis module or a PC-based vision system. This mode offers maximum flexibility for complex applications or individual evaluation logics.

Flexibility through a Variety of Interfaces

Depending on the mode of operation, various interfaces can be used for seamless integration into a wide range of production environments.

Interfaces in “Smart Profile Sensor” Mode

Industrial Ethernet interfaces, including PROFINET, EtherNet/IP, EtherCAT and TCP, can be used for fast connection and reliable communication with PLC systems, robots and other controllers.

Interfaces in “Profile Generator” Mode

Typical interfaces in “Profile Generator” mode are GigE Vision, GenICam, or a Software Development Kit (SDK). This makes it easy to integrate data into standard image processing software or customer-specific applications.

Main Components Explained in Detail: Find Out More!

Detailed information on the laser module, camera and analysis module can be found further down on the page.

Applications of 2D/3D Profile Sensors

Parts measurement

Height inspection

Diameter control

Roundness check

Thickness measurement

Positioning

Weld seam tracking

Weld seam inspection

Gap dimension control

Volume measurement

Angle measurement

Sectors and Industries Which Use 2D/3D Profile Sensors

The requirements in industrial automation are diverse. Whether you are faced with constantly changing weather conditions, intensive cleaning processes, hazardous areas or welding spatter – the wenglor portfolio of 2D/3D profile sensors offers various model variants. These sensors are designed to perform reliably in the harshest conditions, while complying with the technical regulations and quality standards of the industry.
When manufacturing car seats, it is important to ensure that the position of side cushions and spine cushions is identical for each seat. At a test station, car seats are measured from top to bottom with a 2D/3D profile sensor. Contours and filling rates are recorded, symmetries are evaluated and the seams and seat positions, as well as any damage, are detected.

During the production of click parquet, the boards’ quality in terms of geometry has to be assured continuously during operation. However, the milling tools used for this wear out over time, leading to scrap. To reduce this, the lateral edges of the parquet boards are measured to the micrometer by two 2D/3D profile sensors directly after the milling process, and the 2D profile data is processed, visualized and evaluated by a software control unit.

After ice cream cups are filled, it is necessary to check that the attached cardboard lids are present and in the correct position. A 2D/3D profile sensor with IP69K degree of protection uses laser triangulation to detect presence, beaker height and the angle of placed lids over the entire width of production line conveyors. Web-based visualization directly on the system reports the status of the results.

In large logistical centers, the packing volume is of central importance for reducing storage costs, saving filling material and ultimately determining the correct size for the outer packaging. The highest point of the object is determined by a 2D/3D profile sensor before the packaging process. The box is then individually reduced and sealed.

Before maintenance work, such as grinding or milling rails in track beds, can be carried out, both the position of the rails and obstacles such as stones or switches must be detected during operation. Several 2D/3D profile sensors mounted next to each other measure the profile of the track bed in a line. The height profiles are combined and analyzed by software.

In foundries or blast furnaces, steel tubes through which liquid steel passes must be measured with micrometer accuracy for quality control at temperatures of up to 1,300 °C in order to detect their position. A 2D/3D profile sensor which tracks the red-hot tube is installed on the robot arm for this purpose. An appropriate cooling housing enables accurate measurement even at extreme temperatures.

In fully automatic robot welding cells, it is necessary to determine the exact position of joints before the welding process. To do so, a 2D/3D profile sensor is mounted directly in front of the welding torch on the robot, which detects the joint via laser triangulation. The uniVision software determines the guide point and sends it to the control system. A web correction is now carried out using this information and the weld seam is placed.

Laser Module in Detail

How Does a Laser Dot Become a Laser Line?

A laser emits a focused dot beam with a circular cross-section. To create a line from this, the beam is fanned out using special optics consisting of cylinder or Powell lenses. This creates a precise line beam that appears as a clearly defined laser line on the surface of the object.

How Do Cylinder and Powell Lenses Work?

Cylinder Lenses

The light beam (1) is only broken by a cylindrical lens (2) along one axis, thus creating a line from a circular laser dot. The beam originally emitted by the laser usually has a Gaussian-shaped intensity profile. This means that the intensity is highest in the middle and gradually decreases towards the edges. If this point beam is converted into a line (3) with a cylindrical lens, this uneven intensity distribution is retained. The line is significantly brighter in the middle than at the ends.

Powell Lenses

A Powell lens (2) is a specially shaped cylindrical lens. It was developed to create a laser line with a uniform intensity distribution (3) from a Gaussian-shaped laser dot (1). Unlike a simple cylindrical lens, the Powell lens deflects the light so that the center of the beam is less intense and the brightness is balanced along the entire line. This creates a laser line with a so-called flat-top profile, which has uniform illumination and no lighter or darker spots along the line.

What Is the Difference Between Normal Light and Laser Light?

Normal Light

Ordinary light, for example from a light bulb, spreads in many directions and consists of many different wavelengths. This creates a light beam whose light spot diameter becomes increasingly diffuse as the distance increases.

Laser Light

Laser light, on the other hand, is highly focused and consists of one wavelength. All light waves are combined in one direction, which enables a small light spot diameter even at great distances.

Light Sources of 2D/3D Profile Sensors

2D/3D profile sensors use a laser because it creates a precise laser line. The wenglor portfolio includes 2D/3D profile sensors with three different light sources: red, blue and UV. These light sources have different wavelengths and yield optimal measurement results with different material properties and surfaces.
 

Laser (Red)

The wavelength of the red laser is 660 nm. 2D/3D profile sensors with red lasers are very versatile and available in different laser classes.


Laser (Blue)

Blue lasers have wavelengths of 405 nm and 450 nm. These sensors are ideal for inspecting semi-transparent plastic objects, high-gloss metal objects and organic objects.

Laser UV/Red

The wavelength of the UV laser is 375 nm. Sensors with UV/red lasers are used to measure transparent objects such as glass disks or floodlights, provided that the surface reflects UV radiation.

Why Are There Different Laser Wavelengths?

Choosing the right laser wavelength is crucial for a 2D/3D profile sensor’s measurement quality and adaptability to different surfaces, materials and applications. The depth of penetration into the material and the sensitivity of the camera chip play an important role here.

 

Depth of Penetration into the Material

The wavelength affects how deeply the laser light penetrates a material before it is scattered or reflected. Short-wave blue light at 405 nm remains stronger on the surface, providing particularly precise results on transparent, semi-permeable or organic materials such as adhesives, rubber or plastics. Longer wavelengths, such as red light at 660 nm or infrared light at 785–850 nm, penetrate deeper and are better suited for dark, diffuse or metallic surfaces.

Camera Chip Sensitivity

Camera chips, also known as image sensors, have different sensitivities to certain wavelengths depending on their design. If the laser wavelength is optimally matched to the sensitivity curve of the camera chip, the signal strength improves significantly. As a result, shorter exposure times can be used with the same laser power, resulting in higher measuring accuracy and lower measurement uncertainty.

The graphic shows the normalized spectral curve of a 2D/3D profile sensor between 400 and 1,000 nm.

Bandpass Filter: Targeted Light Filtering for Stable Measurement Results

Bandpass filters are optical filters that are precisely matched to the wavelength of the laser used. They only allow light within this narrow spectral range. All other light components, such as ambient light, external illumination or laser beams of a different wavelength, are filtered out reliably. This significantly improves measurement stability and ensures stable edge detection and precise profile contour capturing – even in highly variable light conditions or bright industrial environments. No additional shielding or light control is required. Bandpass filters are integrated directly into the camera’s optical system.

Avoiding interference when operating multiple sensors in parallel

Modern measuring systems often use several 2D/3D profile sensors that work with different laser colors. Bandpass filters are used to prevent mutual interference between the sensors. 2D/3D profile sensors with red lasers have a red bandpass filter that allows only this light through. Sensors with blue lasers, on the other hand, have a blue bandpass filter that only allows blue laser light through. These filters block the laser beams of the other sensor color so that the signals cannot overlap or interfere.

What Impact Does the Color of the Measured Object Have on the Choice of Laser?

Choosing the right laser wavelength depends not only on the optical properties of the sensor, but also on the reflective properties of the object to be measured. The spectral interaction between the laser light and material surface directly influences the profile quality, exposure time and signal strength.

In general, note: The closer the object color is to the wavelength of the laser used, the more light is reflected and the stronger the feedback signal received by the sensor. A red object reflects red laser light much more efficiently than blue light. The result is shorter exposure times, less noise and more stable profile data. Conversely, a red object with blue laser requires significantly longer exposure times, as it absorbs most of the blue light.
 

In addition to the color, the material surface is also important. Light, matte or diffusely reflective materials behave differently than shiny, dark or transparent objects. The performance of the 2D/3D profile sensor can be significantly improved by matching the laser color with the object material. Even challenging surfaces like rubber, glass, high-gloss metals or organic substances can be detected reliably and precisely.

 

Reflectivity of Red Laser Light on Differently Colored Objects

Red Object

Good reflection of the red laser, feedback is very strong

Blue Object

Weak reflection of the red laser, feedback signal is weak

Black Object

Most of the red laser light is absorbed, feedback is moderate

Reflectivity of blue laser light on differently colored objects

Red Object

Weak reflection of the blue laser, feedback signal is weak

Blue Object

Good reflection of the blue laser, feedback is very strong

Black Object

Most of the blue laser light is absorbed, feedback is medium

Choosing the Right Laser Class for 2D/3D Profile Sensors

To achieve optimal measurement performance with 2D/3D profile sensors, choosing the right laser class is crucial – especially with regard to surface properties, working distance, measurement speed and ambient light. wenglor’s 2D/3D profile sensors are available in various laser classes, enabling precise and reliable adaptation to different application cases.

Speed and exposure time
Higher laser powers generate more intense reflections, resulting in shorter exposure times. This is particularly advantageous for fast processes or moving objects.
Object properties
Dark, absorbent or highly scattered surfaces require more light energy to produce sufficient reflection for a stable measurement. Here, higher laser classes are often the better choice.
Distance to object
As the working distance increases, the intensity of the reflected light decreases. More powerful laser classes ensure reliable measurement even at greater distances.
Ambient light conditions
In bright environments or with ambient light interference, a higher laser power improves the signal-to-noise ration – especially with reflective or shiny materials.

Laser Classes of 2D/3D Profile Sensors

The following generally applies to 2D/3D profile sensors: The higher the laser power, the higher the laser class. This poses a greater risk and requires suitable protective measures. Lasers are classified in accordance with DIN EN 60825–1 “Safety of laser equipment”. The hazard potential is evaluated using the wavelength and output power.

DescriptionSafetyApplication
Laser class 2Laser class 2 has a maximum power of 1 mW and is in the wavelength range between 400 and 700 nm.If the eyes are briefly irradiated, laser radiation is harmless, as the natural protective reflex of the eyelids comes into play.Ideal for sensitive surfaces, short distances and easy integration without protective measures.
Laser class 3RThe power of laser class 3R is between 1 and 5 mW at a wavelength range between 302.5 nm and 700 µm.The laser radiation is potentially hazardous to the eyes. A risk assessment is required for operation. Users must be instructed annually and a laser protection officer must be appointed. In addition, the laser area must be marked accordingly and access must be restricted to authorized persons. Depending on the results of the risk assessment, additional protective measures, e.g., wearing laser safety goggles, may be required.Suitable for larger working distances or dark materials.
Laser class 3BClass 3B lasers have a power of 5 to 500 mW and operate in the wavelength range of 302.5 nm to 1 µm.The laser radiation is hazardous to the eyes and possibly also the skin. A risk assessment is absolutely necessary for operation. In addition, users must be instructed annually, a laser protection officer must be appointed, the laser area must be marked, and access must be restricted to authorized persons. The results of the risk assessment determine the necessary protective measures, e.g., wearing laser safety goggles.For particularly demanding environments with difficult surfaces or high ambient brightness.

Safety Features for Higher Laser Classes

For industrial applications with laser classes 3R and 3B, wenglor offers the powerful 2D/3D profile sensors from its MLSL2xxS40 series. These sensors have a built-in laser shut-off that deactivates the laser beam when predefined safety-related conditions are met. The sensor remains in operation when this occurs. This technology meets the requirements of safety standard EN ISO 13849–1:2016 and ensures maximum safety in industrial environments. In combination with the appropriate wenglor safety technology, this means holistic safety solutions for your machines and systems.

 

Integrated Camera in Detail

The camera integrated into the 2D/3D profile sensor is a key component of the optical triangulation principle and ensures precise detection of the projected laser line. The camera essentially consists of two key components: the lens and the camera chip, also known as the image sensor.

Camera Chip

The camera chip converts the incoming light into electrical signals, which are then used to generate digital image information. The size and resolution of the chip affect the measurement detail and precision.

Lens

The lens combines the light and focuses it onto the camera chip. The focal length of the lens has a significant influence on the image section and depth of focus.

Optics and Image Chip – Influence on Measuring Range and Accuracy

The combination of optics and image chip is crucial for the accuracy and measuring range of the sensor. 2D/3D profile sensors can detect smaller details or cover larger areas, depending on the interplay of focal length, sensor size and resolution. Both components are critical to the accuracy and measuring range of the sensor.

Mechanically coupling the sensor housing and precise alignment to the laser module ensure reliable image acquisition without further adjustment being necessary.

Sensor Visual Field

The position at which the reflected laser line is projected onto the CMOS (complementary metal-oxide semiconductor) sensor depends directly on the distance to the object. As the distance increases, the position of the laser line on the CMOS chip (1) changes vertically, allowing height information to be captured.

The different measuring ranges of 2D/3D profile sensors are due to the mechanical format, triangulation angle and respective optics used. The lens systems used determine the visual field of the sensor via their focal length, which is trapezoidal due to the triangulating measuring principle.

The measuring range (2) is divided into three zones – start (3), middle (4) and end (5) – whereby the lateral resolution (x) changes over the depth (z).

At the beginning of the measuring range, the x-resolution is highest due to the visual field’s smaller optical expansion. Eventually, it decreases as larger areas of the object are imaged on the CMOS sensor with a constant number of pixels. This results in a variable lateral resolution, which is specified in the data sheet as a range value.

From an optical perspective, the middle range of the measuring volume provides the best measurement results, as this achieves an optimal compromise between depth of field, focus quality and geometric mapping. 2D/3D profile sensors should therefore be aligned so that the object to be measured is as close as possible to the middle of the specified measuring range.

Camera Image

The camera uses a light-sensitive CMOS sensor consisting of a matrix of pixels. These are arranged in horizontal rows (x) and vertical columns (y). If the laser line hits an object, its reflection is projected onto the CMOS chip by the camera optics. The vertical position of the light intensity in each column (y) provides the respective height information (z) along the profile axis (x). This creates an exact 2D height profile with precise z-resolution.

Camera Image

Camera Image with CMOS Grid and Rows (x) and Columns (y)

What Is the Resolution of a 2D/3D Profile Sensor?

The resolution of a 2D/3D profile sensor is determined by the field of view and the number of pixels of the integrated CMOS sensor.

  • The x-resolution of the sensor is determined by the number of horizontal pixels on the image chip, i.e., the resolution per line. 
  • The z-resolution of the sensor is determined by the number of vertical pixels on the image chip, i.e., the resolution per column.
  • The y-resolution of the sensor indicates the number of profiles per unit length. It does not depend directly on the image chip, but on the relative movement between the 2D/3D profile sensor and object as well as on the sensor’s measurement frequency. A higher measurement frequency with a constant motion speed results in a denser profile recording along the direction of motion and thus a better y-resolution.

More Precision Thanks to Sub-Pixel Technology

Thanks to sub-pixel technology, 2D/3D profile sensors achieve a z-resolution that is many times finer than the size of a single camera pixel. This is because the position of the laser line is determined accurately within one pixel. Instead of simply interpreting the line as one pixel, its brightness gradient is measured over several pixels. Mathematical algorithms can be used to calculate the exact center point, often with fractions of a pixel. For example, a position such as 237.42 can be measured instead of pixel 237. This technology makes even the smallest differences in height visible.

How Does the Field of View Affect the Resolution?

Large Field of View

With a large field of view, the existing pixels are distributed over a larger area. The spatial resolution per pixel decreases, making smaller details more difficult to detect.

Small Field of View

A smaller field of view results in a higher resolution because each pixel covers a smaller area in the sensor’s visual field. Finer structures and details can thus be captured.

How Do the Camera Image and Pixels Become a 2D Height Profile?

The FPGA processor integrated into the 2D/3D profile sensor calculates the entire profile in real time. It analyzes the laser line images captured by the CMOS sensor, extracts the relevant pixels and determines their precise position. This data is converted into a 2D height profile that shows both the lateral (x) and vertical (z) structure of the object along the profile axis. The generated profile data can be used immediately for downstream evaluation or further processing in automation and quality control processes.

Camera Image with CMOS Grid and Rows (x) and Columns (y)

2D Height Profile

From Pixels to Millimeters

To convert the pixels captured by the CMOS sensor into precise metric coordinates, each 2D/3D profile sensor is linearized at the factory. In this process, the sensor is mounted on a high-precision linearization table and precisely aligned to a calibrated reference object. Linearization is done over the entire measuring range and determines the deviation between the pixel coordinates actually detected and the metric data in millimeters.

The resulting correction data is permanently stored in the sensor as a linearization matrix. This compensation ensures that absolute height and position values can be output in millimeters and that any sensor can be used directly in demanding industrial environments without further calibration.

Resolution and Accuracy of 2D/3D Profile Sensors

Resolution

The resolution defines the smallest physical difference that a sensor can still clearly detect and differentiate as a measured value. It thus specifies the minimum sample size with which changes in the measurement signal are detected.

For a feature to be reliably detected, it should ideally be at least five times the resolution of the sensor. This ensures that there are enough image points available to clearly and reliably capture the feature.

 

Accuracy

However, measuring accuracy is not determined solely by resolution. It also depends on various external influences, such as the optical and physical properties of the measured object, reflectivity, the influence of external light, temperature fluctuations, mechanical vibration, the type of mounting and the evaluation algorithms used. Accuracy results from the combination of precision (repeatability under the same conditions) and correctness (deviation of the measured value from the actual reference value) and thus describes to what degree the sensor reliably and correctly depicts the real object.

Parameters for Optimizing Image Acquisition

Frame rate
The frame rate indicates how many frames are captured per time span.
Region of interest (ROI)

The region of interest defines which section of the visual field is used for evaluation or measurement.

Subsampling
Subsampling reduces the number of read pixels in order to reduce the amount of data or increase the speed.

Frame Rate

The CMOS camera in the 2D/3D profile sensor is crucial for the achievable measurement speed. The frame rate indicates how many frames per second the camera can capture. It is expressed in frames per second (fps) or in hertz (Hz).

Since each captured image represents a complete height profile, the camera’s frame rate directly corresponds to the number of measured profiles per second. A high frame rate thus enables a correspondingly high profile frequency.

CMOS camera2D/3D profile sensor
Frames per second (fps)Profiles per second (Hz)
500 fps500 profiles per second or 500 Hz

Region of Interest (ROI)

In high-speed applications, full use of the maximum visual field of a 2D/3D profile sensor can limit the achievable measurement frequency. To counteract this, the image area to be evaluated can be specifically restricted to a region of interest (ROI). The ROI defines the active section of the CMOS sensor used for triangulation evaluation and can be freely parameterized in both the lateral (x) and depth (z) directions. Image areas outside the defined ROI are not read out, nor are they included in the image capture or profile calculation.

Reducing the ROI does not change the optical resolution, it only minimizes the number of pixel rows or columns to be read. This leads to a significant increase in measurement frequency, as less image data needs to be processed. Targeted tailoring of the ROI to the application-relevant object areas makes it possible to obtain optimized data while also ensuring maximum process speed. Note: As small as possible, as large as necessary.

In the animation, the sensor’s entire visual field is indicated with a blue frame. The green frame shows the ROI, i.e., the restricted image area. In order to achieve a better measurement frequency, it is particularly useful to limit the visual field for smaller objects.

Subsampling

With subsampling, the CMOS image sensor is not read in full resolution, rather, only selected pixels are captured at defined intervals, for example every second or third line (vertical) or column (horizontal). This systematic reduction of the pixels to be read significantly reduces the data rate, which can speed up image acquisition and increase measurement frequency. Subsampling is used for targeted reduction of the lateral (x) and/or height (z) resolution without affecting the geometric accuracy of the recorded profiles.
Subsampling is particularly advantageous when full depth of detail is unnecessary or rough contour information is acceptable, e.g., for rapid preselection or for position detection in high-speed applications.
 

Figure 1: Without subsampling
Figure 2: With subsampling

Combined with ROI for Maximum Performance

The highest measurement speed is achieved when subsampling is combined with a targeted restriction of the visual field. By limiting the ROI to a relevant sub-area of the integrated camera, both in the x- and z-direction, only the pixels of the specified measuring range are captured and processed.

Combining ROI and subsampling thus enables very high profile rates with a simultaneously small amount of data. This is particularly beneficial for time-critical applications where speed and efficiency are critical.

Comparison of Region of Interest and Subsampling Settings

ModeSelected pixel countMeasuring rangeResolutionReading speedUsage scenario
Full screenAll pixels (full ROI)Full rangeMaximum detail resolutionLow to mediumPrecise measurements where all image information is needed
ROISub-area (defined)DecreasedUnchanged in active rangeMedium to highFocused measurement on relevant object areas
SubsamplingOnly every nth pixelFull rangeReduced resolutionHighRough measurement, rapid orientation, pre-inspection
ROI + subsamplingFew pixels selectedDecreasedReduced resolution in ROIVery highHighly dynamic applications with clearly defined target ranges

Analysis Module in Detail

The analysis module of the 2D/3D profile sensor processes profiles along an optimized signal processing chain. After detection of the laser line by the CMOS image chip and real-time profile calculation and calibration in the FPGA, the CPU handles the central profile evaluation. This can be done in the two operating modes of “Smart profile sensor” or “Profile generator”.

Smart Profile Sensor

In Smart mode, the entire evaluation is done directly on the 2D/3D profile sensor itself. The machine vision software runs on the sensor and processes the recorded profile data. In this way, measurement-relevant results are calculated and can be provided directly by the sensor. These results, e.g., height deviations, object contours, position detection or tolerance comparisons, are output directly as application-specific measured values to a PLC, higher-level controller or other actuators. No external data processing is required. This reduces system complexity and enables direct evaluation on the device. However, due to the limited computing capacity in Smart mode, the performance is usually lower than the theoretically possible profile rate. If this is the case, “Profile generator” mode is recommended in combination with an external evaluation tool such as uniVision.

Profile Generator

In “Profile generator” mode, the sensor only transmits the 2D profile (x and z data) without making a direct interpretation. The evaluation is then done externally, either within the wenglor ecosystem, e.g., with the wenglor uniVision image processing software on a machine vision controller or by means of independent third-party software on an external industrial PC. This flexibility makes it possible to implement complex evaluations, individual algorithms or application-specific analyses outside the sensor – especially for customer-specific solutions or workflows integrated into existing software landscapes.

Comparison of the Operating Modes of 2D/3D Profile Sensors

Interfaces in Detail

What Are Interfaces?

Interfaces are the basis for communication between sensors, controllers and software. They include the physical connection (hardware interfaces), the transmission rules (protocols) and the software functions (software interfaces) that ensure reliable and flexible integration into industrial systems.

1. Hardware Interfaces – the Physical Connection Level

Hardware interfaces establish the basic physical connection between the 2D/3D profile sensor, control system, network and software. They define the types of electrical and mechanical connections through which data and control commands are transmitted. These physical interfaces – such as Ethernet cables, M12 connectors or digital I/Os – provide the transmission path required for reliable communication.

2. Protocols – Logical Communication Level

 

Protocols define the rules and procedures according to which data is sent via the hardware interfaces. They act as a common “language” for communication and ensure that the data can be correctly interpreted by the emitter and receiver. Protocols define, among other things, how data packets are structured, addressed, sent and received. Different types of transmission are used depending on the required speed, reliability and real-time capability.

3. Software interfaces – Application Level

 

Software interfaces enable sensor data to be controlled, configured and evaluated by higher-level systems or individual applications. They define the logical access points and communication methods through which software solutions can access sensor data or use sensor functions. These include APIs, web services, configuration protocols and standardized interfaces that allow flexible integration into different software environments. Software interfaces abstract the complexity of data communication, thus facilitating integration into individual systems and software solutions.

What Interfaces Do 2D/3D Profile Sensors Have?

Hardware Interfaces

  • Digital I/Os (digital input/output, encoder inputs)
  • Ethernet

Protocols

  • TCP/IP
  • UDP/IP
  • GigE Vision

Software Interfaces

  • GigE Vision / GenICam API
  • wenglor uniVision
  • Software Development Kit (SDK)

Example Interaction Between the Three Interface Levels

A 2D/3D profile sensor with an Ethernet interface establishes the connection to the network or controller. A TCP/UDP or GigE Vision protocol then determines how the profile data or control commands are transmitted. The software interface decides how the application communicates with the sensor, interprets results or triggers commands.

Hardware Interfaces of 2D/3D Profile Sensors

Digital I/O Interfaces

Digital inputs and outputs make it possible to directly control and synchronize 2D/3D profile sensors in industrial processes.

The digital input allows for the precise timing of measurements triggered by external control signals. This is particularly relevant for belt-based or clocked processes. For example, measurement can start as soon as a product reaches a certain location on the conveyor belt and the sensor receives a corresponding signal.

Digital outputs are used to output synchronization signals in order to precisely trigger multiple 2D/3D profile sensors, thereby enabling synchronized measurement. Evaluation results, status messages or events, e.g., good or bad part detection, can also be forwarded to external systems via the digital output.
The encoder inputs of 2D/3D profile sensors enable precise measurement that is adapted to the actual object’s movement. Using hardware encoder signals, movements are precisely translated into profile positions.

The advantage of an encoder is that it automatically takes into account the speed of moving objects and adjusts the image acquisition accordingly. This results in uniform and precise height profiles even with fluctuating movement. In contrast, a fixed trigger starts the image acquisition at a constant time, regardless of the object’s speed. This can result in inaccuracies.

Application Example With and Without Encoder

Without encoders, there is visible distortion in the detected profiles when a conveyor belt starts or slows, as the trigger frequency no longer matches the object’s movement. With encoders, on the other hand, the profile geometry remains correct even when the belt speed changes.

Application Example with Encoder

With encoders, on the other hand, the profile geometry remains correct even when the belt speed changes.

Ethernet Interface

The Ethernet interface (e.g., RJ45, Gigabit Ethernet) forms the basis for communication between the sensor and external system. This interface is used to send the large amounts of data from the height profiles as well as to configure, visualize, control and synchronize the sensor. Depending on the mode of operation and protocol, it is possible to transmit profiles or already evaluated results.

Advantages of Ethernet-Based Connection

High data rates for rapid transmission of profiles
Compatibility with standard protocols such as TCP/IP, UDP, GigE Vision, GenICam and PROFINET
Easy integration into existing network infrastructures

Overview of Protocols and Software Interfaces

2D/3D profile sensors are available in the “Smart Profile Sensor” and “Profile Generator” operating modes. Depending on the selected mode of operation, a suitable communication interface can be selected. This means that the sensor solutions can be specifically adapted to the control concepts, data flows and real-time requirements of the respective application.

Smart Profile Sensor

In this mode, the entire evaluation is done directly on the sensor. Communication with the controller is usually done via digital outputs or Ethernet (TCP). Because of the embedded evaluation, this mode is particularly space- and cost-efficient, but the computing capacity is limited. The combination of multiple sensors is not possible in Smart mode. The evaluation is always done sensor-by-sensor in the respective measuring range. Continuous, coherent measurement across several sensors is not possible.

Profile Generator

In this mode, the sensor acts as a powerful “profile supplier” and sends the generated 2D profiles to an external industrial PC by means of standardized interfaces or an SDK. There, profiles are further processed using image processing software. This mode offers maximum flexibility, scalability and performance. For example, it is possible to synchronize several sensors and evaluate them from one place.

Complete Profile Detection with VisionApp 360

Using the VisionApp 360 software, multiple 2D/3D profile sensors can be combined to create a common 2D height profile from individual measurements. To do so, the sensors are aligned and calibrated in place so that their individual coordinate systems are converted into one uniform, higher-level coordinate system. In the next step, the detected individual profiles of the sensors are merged into one coherent overall profile. This can then be used for further processing.

Typical Interfaces and Their Use Depending on Mode of Operation

Standard Interfaces for Maximum Compatibility

Integration Regardless of Manufacturer

Devices from different providers can be seamlessly integrated into one common system.

Software Compatibility

2D/3D profile sensors can be connected directly to common software solutions.

Investment Protection

Compatibility with established image processing libraries and hardware components ensures the long-term use of existing systems.

Future-Proofing

The continuous further development of standards facilitates the expansion of existing systems.

Maximum Control with Manufacturer-Specific SDKs

Optimal Performance Thanks to Native Connection

Direct programming without standardized intermediate levels makes it possible to implement processes much more efficiently as well as to conserve resources. This is particularly advantageous with high frame rates or large amounts of data.

Individual Integration into Your Own Software Landscape

SDKs include APIs for different programming languages (e.g., C++, C#, or Python), enabling full integration with customer-specific software, graphical user interfaces (GUIs), or control environments.

Rapid Development with Example Code and Tools

Modern SDKs include practical code examples, libraries and debugging tools to accelerate development and make it easy to get started.

In Comparison: Standard Interfaces vs. Manufacturer-Specific SDKs/APIs

FeatureStandard interfacesManufacturer-specific SDK/API
CompatibilityHigh (across devices, manufacturer-neutral)Can only be used with devices from the same manufacturer
Integration effortLow, thanks to standardizationHigher, requires knowledge of manufacturer-specific architecture
Flexibility / functional scopeLimited to standardized functions*Very high, access to deeper functions and parameterization
Future-proofing / maintenanceExcellent long-term availability thanks to standardizationDepends on manufacturer support and software maintenance

* Application-specific functions can be integrated, even within standardized interfaces. This allows for customization without compromising compatibility with existing systems or protocols.

When Should You Choose Standard Interfaces or Manufacturer-Specific SDKs/APIs?

  • Standard interfaces are ideal for easy integration, high compatibility and connection with existing third-party software solutions.

  • The SDK is the right choice when you need maximum control, customization or special features, such as direct sensor control or development of custom software solutions.
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