IDEC DATAVS2 Series - Manual (Page 76)

SVS2 Series Instruction Manual
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16.2. ► Machine vision
This is a specific branch of Computer Vision (or "artificial vision").
Computer vision is a generic concept which applies to all processes aimed at extracting information
from images. On the other hand, machine vision has a specific purpose, i.e. control the operation of
equipment and machinery in industrial applications (such as manufacturing lines or goods handling
applications).
In order to perform this task, machine vision equipment features stand-alone processing capabilities,
digital inputs and outputs, and dedicated peripherals such as photocells and/or a communication
network that allows communication with other similar devices.
In the SVS2 system, sensor vision serves the purpose of inspecting products in order to:
o
detect missing or incomplete parts;
o
read bar codes or datamatrix information;
o
take measurements.
16.3. ► Lighting Conditions Setup
Lighting conditions are a critical aspect in all the machine vision tasks, thus they have to be carefully
set and preserved during the whole inspection process.
The goal of this section is to briefly describe some important considerations about lighting conditions,
easily suitable in many typical machine vision tasks.
- Keep lighting constant into the scene.
Lighting intensity has to be maintained constant as much as possible, avoiding variations
due to ambient light, sunlight or other external light source. External light source may lead to
a failure inspection. Suppressing the external light effects can prevent such failures. It is
possible that the sensor internal illuminator is not effective enough and an external
illuminator have to be used instead. An alternative solution can make use of panels or any
physical barrier to mask the inspection area.
- Keep lighting consistent into the scene.
Make sure that the whole scene receives an uniform illumination to avoid very bright spots or
shadows. Moreover, make sure that the target-objects are well contrasted in their features
and well separated from the background.
- Place the light on the right position.
Adjust the best distance between the light source, the sensor and the target-object. Make
sure that the light source has the proper brightness intensity to avoid the saturation of some
area of the scene.
- Illumination with reflective surfaces
Experimental tests have demonstrated the inefficacy of the SVS internal illuminator
whenever the target-objects have a reflective surface. The reflected light causes the
saturation of some area of the scene. In these cases is recommended to use an external
source of illumination.