Machine Vision Lighting
Without good lighting your vision system will never see anything! Therefore identifying the correct lighting technique to use within an inspection solution is vital to the success on the solution.
Multipix have trained staff that are experts in this field. Multipix not only have a wealth of knowledge but a huge array of lighting at our disposal. Including ranges from, LEIMAC, Moritex, Genesi, DCM, and Spectrum Illumination.
Colour & Contrast
Why is colour so important to illumination? The Electromagnetic Spectrum is the entire range of electromagnetic wavelengths or put another way, it is the entire range of light seen and unseen!
Humans associate daily with a very small section of this range, the ‘visible band’.
Wavelength Spectrum
- Although the majority of machine vision applications are in the visible band of light, many are also using X-ray, UltraViolet and Infra-Red.
- The types of radiation that occur in different parts of the spectrum have different uses and dangers
- The sensor used in a camera will determine how responsive it is at a particular wavelength
- IR has a large wavelength that is visible and can transmit further into certain material such as semi-conductors, paper and other organic materials.
Use colour to create more contrast
Using the light spectrum opposite will make a feature appear darker. Using the same light spectrum will make a part feature appear lighter.
- If the part feature you want to make darker is red, use a green light
- Use a green light to make a green feature appear lighter
This technique is commonly used to make image processing more robust and reliable.
Traditional Lighting Examples
Ring Light
Versatile and common lighting solution. Available as direct or indirect and with low angle options for illuminating defects on shiny surfaces.
Back Light
Delivers broad, high-quality diffused light, providing sharp contrast to outline the shape of a component and view openings such as drilled holes.
Dome Light
Provides practical and cost effective solutions illuminating the surface of an object uniformly by reflecting 360 degrees of light. Ideal for shiny or bumpy surfaces.
Darkfield Light
Provides 360-degree illumination from a shallow angle to ensure that the LEDs are not reflected even on shiny surfaces. Dramatically enhances the contrast of surface features such as laser-embossed, engraved marks or surface defects.
Coaxial Light
Provides diffused, uniform illumination for flat specular surfaces. Can be a separate unit or integrated in suitable lenses to offer illumination within the cameras optical path. Ideal for imaging reflective surfaces, including wafers, metal surfaces, film, liquid crystal and glass.
Line Light
Ideal for linescan camera applications where very intense and uniform illumination is required over a wide field of view.
Beyond traditional methods there are many special lighting techniques.
The LEIMAC flat dome is a superb example of advances in lighting techniques and technology:
Another would be Infra-Red illumination: IR lighting can be used to ‘eliminate’ colour information. Or create high contrast especially for items that are difficult to view in visible light.
Lasers
Lasers are another source of illumination that is often over-looked.
They are typically used for alignment and 3D profiling but can also be used as a source of monochromatic light.