Defect detection on encoder wheels
Case History Heinen
The application
The aim of the project was to detect different types of defects on the surface of film encoder wheels such as impurities on the tracks, small scratches as well as imperfections occurred during the glass forming process.
The goal was also to measure the dimensions of some features of the encoders like gaps, angles and incorrect distances. At Opto Engineering®, we found the detection of these problems very challenging.
“We required high-resolution measurement and high-level scratch detection capabilities”, says Peters. “This system was intended to discover different types of scratches for individual disc sizes. The biggest challenge in this application is to be able to robustly detect the smallest defects within a large field of view. In order to achieve this, a careful choice of the illumination strategy was required”.
Accuracy is critical for this kind of inspection, as Peters explains: “Our customers sell very precise encoder discs in different sizes from 1mm diameter to 100mm in diameter. Their function is to keep accuracy in some of the common machine vision applications, for example motion positioning and position detection: we have a huge responsibility because with a faulty disc these processes might fail!
Setting up the feasibility study
If the setup project is a key part of designing a new measurement machine, the test phase is just as important. Determining what tests to carry out and how to analyze the results is paramount to confirm the validity of the proposed solution and to achieve the best possible system performance.
A complete setup including a high-resolution camera, a large field of view telecentric lens for large format sensors and the combination of three illumination geometries was the starting point to solve this application.
In fact, the new Opto Engineering® high resolution cameras combined with our large format telecentric lenses made it possible to achieve very high pixel count over a large field of view.
Having access to the large selection of LED illuminators offered by Opto Engineering® was an essential resource to properly identify different kinds of defects using different illumination strategies.
With our machine vision software “FabImage®” we were then able to successfully process the images.
Camera:
- COE71MUSB3IR-F
Area scan camera CMOS, USB3,10000 x 7094, monochrome, 3fps, IR Cut filter, F-mount
Optics:
- TC16M120
Telecentric lens for 35 mm detectors,magnification 0.289 x, F-mount
Lights:
- LTRN120NW
Ring LED illuminator, inner diameter 180 mm,straight type, white - LTBC114114-G
Continuos LED backlight,114x114 illumination area, green - LTZZO170-75-3-W-24V
LED low angle ring light,3 LED rows, outer diameter 175 mm, 75°, white, 24V
Software:
- FIS-PRO
FabImage® Studio Professional
Heinen
Why Opto Engineering®?
The study proved the possibility to efficiently perform a complete quality check of the samples. The proposed solutions at each step of the process allowed to reduce time and cost, a paramount aspect in every industrial application. Opto Engineering® was able to provide all the machine vision components needed to perform this task thanks to its wide product portfolio. Furthermore, thanks to a global network of well-equipped vision laboratories and highly skilled tech support specialists, we can provide competent guidance to customers in choosing and implementing the best possible product bundle for any machine vision task.