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Illumination

Illumination is the key to any visual inspection system. Cameras are far less versatile than the human eye, and the lighting conditions need to be optimised to detect the necessary detail. The purpose is to enhance the contrast of the object in a way that the feature is detectable to the machine vision system. The interaction of the light with the surface, i.e. which portion is absorbed and which is reflected back to the camera is very important. Careful consideration can avoid the need for expensive software to enhance the image.

Machine vision illumination can be split into three types; LED illumination, fibre optic and laser. Please click on an image below to be directed to the area of interest.

LED illumination
LED – With the advent of high intensity LED’s these sources provide the most appropriate solution for most applications. They produce high light intensity stable light at a relatively low cost and have a typical unit life of up to 100,000 hours.
Fibre Optic ‘cold light’– Uses an extremely bright lamp (either halogen or metal halide) in an enclosure, with a fibre optic light guide to take the light to the target. Advantages include the fact that no direct heat is delivered to the target and the light is very intense and continuous. Disadvantages include a shorter unit life.
Laser – Used in structured lighting applications, to assist with depth measurements, 3D inspection and equipment alignment.
Please see our laser section for more information.

Illumination Techniques

Below are the standard illumination techniques used in machine vision. Please call us if you are unsure of the best technique for your application.

Ringlight

Great for standard applications, and provides a uniform even illumination. Not suitable for highly reflective surfaces. Sizes to fit all standard microscope objectives and larger sizes ranging from 44mm to 202mm.

Darkfield ringlight

Suitable for highly reflective surfaces and makes surface structures visible. Available in sizes from 44mm to 281mm with various cut-off angles.

Domelight

Provides non-directional diffused light, which eliminates glares and shadows. Available in sizes from 44mm to 202mm

Lightline

Available in pretty much any length needed. We also have a range of water-cooled LED light lines, which provide as much intensity as the fibre optic equivalent.

Coaxial

Only allows reflection from the flat surface into the camera which provides good contrast with glossy objects.

Backlight

Provides sharp silhouettes of objects for edge detection and even illumination for opaque and transparent targets. Sizes range from 51x84mm up to 195x444mm.

There are a number of points to consider when determining the type of illumination for a particular job:

  • Is the application colour of monochrome?
  • How large is the area to be illuminated?
  • Is it a high or low speed application?
  • What does the service life of the light need to be?
  • What is the nature of the object (size, surface) and what is the feature on the object?
  • Are there any environmental or mechanical constraints?