What Is a 2D/3D Profile Sensor?
2D/3D profile sensors are available in two different performance classes:
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
2D/3D Profile Sensors Stainless Steel
2D/3D Profile Sensors for Bending Machines
The Triangulation Principle
Creating a 2D Height Profile h3>
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?
From 2D Height Profile to 3D Point Cloud h3>
Coordinate System of a 2D/3D Profile Sensor
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) h4>
y-Axis (Feed Direction) h4>
z-Axis (Height/Distance) h4>
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 h4>
Sensor Tilt h4>
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.
Shadowing
How to Prevent Shadowing?
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.
Main Components of a 2D/3D Profile Sensor at a Glance
The performance of the laser module is largely determined by the laser wavelength and laser class.
Laser Wavelength
Laser Class
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.
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 h4>
Mode of Operation: Profile Generator h4>
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
Interfaces in “Profile Generator” Mode
Main Components Explained in Detail: Find Out More!
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
Laser Module in Detail
How Does a Laser Dot Become a Laser Line?
How Do Cylinder and Powell Lenses Work?
Cylinder Lenses h4>
Powell Lenses h4>
What Is the Difference Between Normal Light and Laser Light?
Normal Light h4>
Laser Light h4>
Light Sources of 2D/3D Profile Sensors
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 h4>
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 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 h4>
Blue Object h4>
Black Object h4>
Reflectivity of blue laser light on differently colored objects
Red Object h4>
Weak reflection of the blue laser, feedback signal is weak
Blue Object h4>
Good reflection of the blue laser, feedback is very strong
Black Object h4>
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.
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.
| Description | Safety | Application | |
|---|---|---|---|
| Laser class 2 | Laser 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 3R | The 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 3B | Class 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 h4>
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
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.
Camera Image
Camera Image h4>
Camera Image with CMOS Grid and Rows (x) and Columns (y) h4>
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 h4>
How Does the Field of View Affect the Resolution?
Large Field of View
Small Field of View
How Do the Camera Image and Pixels Become a 2D Height Profile?
Camera Image with CMOS Grid and Rows (x) and Columns (y) h4>
2D Height Profile h4>
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.
Accuracy h4>
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
The region of interest defines which section of the visual field is used for evaluation or measurement.
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 camera | 2D/3D profile sensor |
|---|---|
| Frames per second (fps) | Profiles per second (Hz) |
| 500 fps | 500 profiles per second or 500 Hz |
Region of Interest (ROI)
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
Figure 1: Without subsampling
Figure 2: With subsampling
Combined with ROI for Maximum Performance h4>
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
| Mode | Selected pixel count | Measuring range | Resolution | Reading speed | Usage scenario |
|---|---|---|---|---|---|
| Full screen | All pixels (full ROI) | Full range | Maximum detail resolution | Low to medium | Precise measurements where all image information is needed |
| ROI | Sub-area (defined) | Decreased | Unchanged in active range | Medium to high | Focused measurement on relevant object areas |
| Subsampling | Only every nth pixel | Full range | Reduced resolution | High | Rough measurement, rapid orientation, pre-inspection |
| ROI + subsampling | Few pixels selected | Decreased | Reduced resolution in ROI | Very high | Highly 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 h3>
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 h3>
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
| Mode of operation | Result | Further processing | Special feature |
|---|---|---|---|
| Smart profile sensor | Measured values | Evaluation is done on the 2D/3D profile sensor |
|
| Profile generator | 2D profiles | Processed with external software |
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Smart profile sensor
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|---|---|---|
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Measured values
|
Evaluation is done on the 2D/3D profile sensor
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|
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Profile generator
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2D profiles
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Processed with external software
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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
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.
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 h4>
Application Example with Encoder h4>
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 h5>
Compatibility with standard protocols such as TCP/IP, UDP, GigE Vision, GenICam and PROFINET h5>
Easy integration into existing network infrastructures h5>
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 h4>
Profile Generator h4>
Complete Profile Detection with VisionApp 360 h4>
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
| Interface / protocol | Smart profile sensor | Profile generator | Transmitted data |
|---|---|---|---|
| Digital I/Os | Triggers / results | ||
| TCP/IP | Profile data / results | ||
| GigE Vision | Profile data | ||
| GenICam | Profile data, control | ||
| SDK | Profile data, control |
Standard Interfaces for Maximum Compatibility
Integration Regardless of Manufacturer
Software Compatibility
Investment Protection
Compatibility with established image processing libraries and hardware components ensures the long-term use of existing systems.
Future-Proofing
Maximum Control with Manufacturer-Specific SDKs
Optimal Performance Thanks to Native Connection
Individual Integration into Your Own Software Landscape
Rapid Development with Example Code and Tools
In Comparison: Standard Interfaces vs. Manufacturer-Specific SDKs/APIs
| Feature | Standard interfaces | Manufacturer-specific SDK/API |
|---|---|---|
| Compatibility | High (across devices, manufacturer-neutral) | Can only be used with devices from the same manufacturer |
| Integration effort | Low, thanks to standardization | Higher, requires knowledge of manufacturer-specific architecture |
| Flexibility / functional scope | Limited to standardized functions* | Very high, access to deeper functions and parameterization |
| Future-proofing / maintenance | Excellent long-term availability thanks to standardization | Depends 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.