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Technology of Machine Vision Cameras

Machine vision cameras play a critical role in vision applications, especially in automated quality control. In combination with machine vision controllers and 2D image processing software, the high-resolution image data is analyzed, and errors as well as irregularities in production processes are identified.

What Is a Machine Vision Camera?

A machine vision camera, also known as an industrial camera, is a key part of a 2D image processing system. Its main function is to capture images, which are then processed by a combination of hardware and software. The information obtained is prepared for various applications.

A typical example of an image processing application in a manufacturing system is quality control, presence control and completeness control. This involves analyzing a specific feature of a part that is produced on an assembly line. In this way, it can be checked whether the part meets the quality criteria or, if necessary, must be sorted out.

The camera is part of the image processing system. This consists of the following components:

Main Components of 2D Image Processing Systems

Selection Guide for the Right Lens

Find the right lens for your industrial camera easily and automatically using the Vision Calculator:

The Difference Between Machine Vision Cameras and Smart Cameras

Machine Vision Cameras

  • Image evaluation takes place via the machine vision controller and the image processing software

  • Multiple cameras can be connected to a single machine vision controller

  • Faster process times thanks to high computing power of the machine vision controller

  • Suitable for very high resolution inspection tasks

  • Compact camera design



 

Smart Cameras

  • Image capture and evaluation takes place in the smart camera

  • Data output via integrated interfaces

  • Optionally integrated illumination technology

  • No additional controller required



 

Applications of Machine Vision Cameras

Position Check

Robot Positioning

Parts Measurement

Quality Control

Presence Check

Process Monitoring

Code Reading

Reliable Solution for Cross-Industry Applications

Automotive Industry

  • Quality inspection of car interior doors

  • Quality inspection of engine blocks

  • Position detection for automated tightening

Electronics Industry

  • Position check of PCBs

  • Checking the alignment of components

  • Inspection of plug connectors and cables

Packaging Industry

  • Check packages for damage, contamination or missing labels

  • Label inspection of packaging

  • Minimum shelf life test on PET bottles

Food Industry

  • Orientation of beverage cans 

  • Label check on packaging

  • Tethered cap inspection

This Is the Difference Between Surface and Line Cameras

The following table summarizes the main differences between surface and line cameras:

Surface cameras

Image capture of complete 2D surfaces (with one capture)
High image quality
Ideal for stationary objects
Suitable for general image processing



Line Cameras

Image capture takes place line by line (movement is necessary to capture the object)
Image quality dependent on motion and time of image capture
Ideal for applications with moving objects and endless materials 
High speed

Operating Orinciple of CMOS Sensors with Global or Rolling Shutter

CMOS image sensors have two exposure methods that control how an image is captured and read. These procedures determine the exposure time and thus the amount of light that is converted into electrons as a value in the camera sensor. A distinction is made between global shutter and rolling shutter:

Global Shutter

Entire image area is exposed simultaneously 
Suitable for static as well as dynamic applications
No image distortion on moving objects

Rolling Shutter

Lines are exposed with a time offset
For static applications
Image distortions due to fast object movements (rolling shutter effect)
Capturing still images 

The Rolling Shutter Effect

With the rolling shutter, the exposure time is the same for all pixels of the sensor, but the exposure of the individual lines takes place one after the other with a time delay. The rolling shutter effect occurs when an object moves faster than the exposure and read time, causing the image to be distorted due to exposure.

Left: Global shutter, Right: Rolling shutter

Monochrome or Color Camera? Which Do I Use When?

Actual Image

Image Capture with a Monochrome Camera

A monochrome camera can distinguish objects from the background.

Image Capture with a Color Camera

A color camera is able to distinguish objects from each other and from the background.

In industrial image processing, a distinction is made between monochrome and color cameras. Monochrome cameras capture grayscale and focus on the differences in brightness in the image. This makes them particularly suitable for applications that require fine contrasts and details, such as when inspecting surfaces or measuring objects.

Color cameras, on the other hand, can capture color information, allowing them to capture surfaces more accurately. They analyze the entire color spectrum, providing more detailed and versatile image reproduction. This makes them ideal for applications where color plays an important role, such as in product quality control, where color differences can indicate material defects.

What to Consider When Installing Machine Vision Cameras

To ensure reliable image capture, the following instructions must be observed when adjusting the industrial camera.
In addition to the optimal orientation of the camera, the positioning of the illumination plays an important role. The shape of the object to be examined is key for how the light reaches the camera to create the highest possible contrast. It is important to note, for example, the angle and the resulting reflections. 

The Machine Vision Camera Interface

An Ethernet interface for industrial cameras allows image data to be transferred over a network. This interface is commonly used in industrial image processing to connect cameras to machine vision controllers or other devices.

Gigabit Ethernet (GigE)

Gigabit Ethernet (GigE) is an Ethernet technology that enables data transfer rates of up to 1 Gigabit per second (1 Gbit/s). The main features of Gigabit Ethernet in connection with industrial cameras are:
 
  • Fast transfer of large amounts of image data

  • Easy integration thanks to protocol standard

  • Multiple cameras can be operated in a network


It is also possible to connect the machine vision camera via a cable using PoE (Power over Ethernet), which means that both power supply and data transfer take place via a single connection.


Resolution

The spatial resolution of a sensor indicates the number of pixels: the higher the resolution, the smaller the pixel size and the finer the details that can be detected. Sensors can have different resolutions with the same dimensions because the pixel size can vary. 

Frame Rate

The frame rate indicates the number of complete frames a camera captures per second. A higher frame rate enables many images to be captured in fast-paced applications.

Exposure Time

The exposure time determines how much light falls on the CMOS sensor and thus affects the brightness and sharpness of the recorded image. A longer exposure time leads to brighter images, but can also cause motion blur and increased image noise. A short exposure time enables fast applications and reduces the associated motion blur. 

The Right Resolution for Every Application

ResolutionAccuracyExamples
1.6 MPApplications that do not require extremely high resolutionOptical character recognition, assembly control, presence check
5 MPApplications requiring medium level of detailInspection of packaging
12 MPApplications requiring high precisionInspection of fine mechanical parts
24 MPApplications requiring very high resolution and attention to detailChecking PCBs for faulty components
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