LED backlighting systems are becoming increasingly widespread and popular in machine vision applications.
Thanks to their low cost, high energy efficiency and long service life, they are the ideal choice for many applications in which an area needs to be illuminated uniformly.
In particular, LED backlighting is now the preferred choice for analysing the shape and size of objects in a variety of applications.
LED backlighting is a lighting method in which the light source is located behind an object, rather than in front of it as with front lighting. This type of lighting is particularly useful in the machine vision sector for analysing the size and shape of objects.
Using LED backlights makes it possible to obtain high-resolution images of objects, thanks to the reduction of shadow and reflection effects.
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Backlighting in vision systems
In the field of industrial automation and quality control, machine vision systems play an increasingly central role in ensuring precision, reliability and traceability. Lighting is a fundamental element for the correct operation of these systems. In particular, LED backlighting is an effective technical solution in many applications that require high-contrast images and well-defined contours. This article examines the characteristics of LED backlighting, the advantages it offers in industrial settings and its main technical applications.
What LED backlighting is
Backlighting, or backlight, consists of a light source placed behind the object to be inspected, with the camera positioned on the opposite side from the source. This produces a shadow projection of the object, which highlights its profile and allows its contours to be detected precisely.
LED-based backlighting systems use an array of light-emitting diodes arranged evenly, often combined with an optical diffuser, to ensure uniform illumination over the entire area of interest. LEDs offer a long operating life, low maintenance and the ability to be controlled electronically with great precision, including in strobe mode.
Technical advantages of LED backlighting
Using LEDs as the source for backlighting offers numerous technical advantages:
- Light uniformity: the combination of high-quality LEDs and optimised diffusers produces an illumination field free of gradients, which is essential for metrological measurement or dimensional verification applications.
- High contrast: backlighting produces binary (black/white) images with sharp profiles, ideal for silhouette recognition, diameter measurement or presence/absence checks.
- Reduction of shadows and reflections: since the object is viewed in silhouette, the influence of surface reflection is eliminated, which is particularly useful for glossy or translucent materials.
- Operational flexibility: LED systems can be driven in direct current or pulsed mode, synchronised with the vision system for high-speed applications.
- Energy efficiency and service life: compared with other lighting technologies, LEDs consume less energy and last longer, reducing maintenance costs.
Design considerations
Selecting and integrating an LED backlighting system requires some design assessments:
- Size of the area to be illuminated: the backlight surface must be correctly sized in relation to the object to be analysed and the camera’s field of view.
- Light colour: red or white light is generally used, but in some applications infrared light or other wavelengths can be useful to improve contrast.
- Synchronisation: in high-speed systems or in environments with variable light, it is often necessary to synchronise the backlight with the acquisition system to ensure consistency and repeatability.
- Heat dissipation: LEDs generate heat, and correct thermal management (with heat sinks or forced ventilation) is essential to ensure stability and service life.
Industrial applications
LED backlighting is particularly suitable for applications where the shape or edges of an object must be detected precisely. Some examples include:
- Dimensional inspection: verification of diameters, thicknesses, lengths or complex geometries using optical measurement systems.
- Defect detection: identification of burrs, non-compliant holes, breakages or missing parts through profile analysis.
- Presence/absence checks: verification of the correct insertion of components during assembly.
- Inspection of translucent objects: analysis of plastic or glass materials which, if lit from the front, would show unwanted reflections.
- Packaging and pharmaceutical sector: verification of correct filling or of the positioning of labels and caps.
Conclusions
LED backlighting is an established and extremely useful technology in the field of industrial machine vision. Thanks to its technical characteristics, it enables precise, repeatable inspections that are easy to integrate into automation processes. Choosing the most suitable lighting system remains a crucial stage in the design of a vision system, and backlighting has a wide range of applications wherever the profile and geometry of the object to be analysed are decisive for quality control.
Products used in this application
DL1 series LED bar illuminators
DL5 series high intensity LED matrix illuminators
DL2 series LED bar illuminators
BL4 series LED backlight illuminators
FD2 series flat dome LED illuminators
DC7 series ring LED illuminators
DC3 series high intensity LED ring illuminators
DC2 series low-angle LED ring illuminators
Further information and contacts
Systems and sensor integration division: www.roder.it
Machine vision division partner: www.rodervision.com
Standard instruments division partner: www.innovacheck.com
More about RODER SRL: about us
Contact for general information: info@roder.it
The information contained on this web page is provided for information purposes only. Although it has been compiled with the greatest care, it does not constitute a contractual offer or a binding commitment to supply. It may contain transcription or translation errors, or typographical errors. For precise and up-to-date information, please contact our company directly.
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