PRECISION LED LIGHTING FOR VISION AND IMAGING


 

 

T he lighting is a critical factor for machine vision successful inspections. From selecting the best lighting options to configuring them in the most optimal setups, customizing lighting for your applications can help produce better results. Unlike everyday smartphone photography, which is optimized for the human eye, machine vision uses lighting to optimize how objects appear to the camera’s sensors. The most successful machine vision applications use lighting that highlights feature of interest while minimizing visual noise.

Why lighting is so important for Machine Vision?

At a basic level, cameras contain sensors that capture incoming light as images. While most photos are typically captured for human review, machine vision applications look at images differently, and they typically perform best on high-contrast images. The central goals of lighting are to highlight features of interest and reduce the focus on the rest of the image.
Lighting is one of the most impactful yet customizable elements of machine vision. We’ve seen numerous customers succeed with our lighting solutions, and we’ve gathered some best practices to show how they can work for your product.
Two main considerations factor into lighting decisions:

  • Setup environment — There is an ideal lighting solution for any environment. Space constraints, levels of ambient lighting, support structures, conveyor speed, and other variables in the immediate inspection area influence what lighting products and configurations should be used
  • Object factors — Shape, material, size, color, reflectivity, inspection elements, and other characteristics of the object inform decisions around lighting options

Since many parameters must be considered, the choice can be difficult and sometimes the wisest advice is to perform feasibility studies with different light types to reveal the features of interest. On the other hand, there are several simple rules and good practices that can help select the proper lights and improve the image quality.

For every application, the main objectives are the following:

  • Maximizing the contrast of the features that must be inspected or measured
  • Minimizing the contrast of the features of no interest
  • Getting rid of unwanted variations caused by :
    – Ambient light
    – Differences between items that are non-relevant to the inspection task

All V5 Group lighting options are available for even greater flexibility. Here are the types of lights we offer:

Multi-angle line light source

High-speed detection lighting for flat transparent glass scratches, Inspections of plastic containers, semiconductor appearance characters such as IC, PCB, packaging appearance, product label, Broken tablet detection, general appearance detection.

Ring light source

High-angle direct illumination and Low-angle ring lights bright circular light typically used to provide directional lighting. Plastic container inspection, microscope illumination. Inspections of semiconductor appearance characters such as IC, PCB, packaging appearance, product label, tablet-damage/absence

Coaxial Lights series

Inspections of highly reflective surface scratch, chip and silicon wafer damage, mark positioning, barcode recognition, laser labeling character, QR code recognition, imprinted characters on metal surfaces, bearings and beverage cans, QR code imprinted on metal and glass plates.

Line lights series

High-speed detection lighting for flat transparent glass scratches, extremely high frequency in order to avoid flickering.

Bar Lights

Provide direct light from an emitting part equipped with LEDS In straight lines

Applications:

Various inspections for reading text, Visual inspection for damage on long and thin workpiece.

Combined Bar Lights

Free angle adjustment. Intensity of each light can be controlled independently.

Applications: Character recognition and defects inspection for large square

illumination.

Defuse lights series

Defuse light provides indirect illumination from an inner conical or square surface, which allows a workpiece to be uniformly illuminated from all angles, resulting in excellent illumination of the inspected object without creating any unwanted glare, hotspots, or shadows from reflective materials. Ideal for objects with glossy, non-flat surfaces, foil-wrapped objects, or mixed reflectivity samples.

UV Lights

UV light are used to inspect fluorescent signs and materials for security and safety applications

IR Lights

IR wavelengths of 850nm and 940nm (also called NIR – Near InfraRed) are commonly used in machine vision. IR can help reduce color of objects. IR can reduce glare and reflections. IR has a longer wavelength than visible light which usually results in a greater transmission of light into a material. A high transmission can result in IR transmitting thru materials like paper, cloth and plastic. This makes IR a good light source for inspecting fill levels in packaging. IR wavelengths react differently on materials and coatings than visible light. Certain defects and flaw detection can be identified with IR where visible light did not work. Testing IR on your part may be the solution.

AOI Lights

Illuminating in multiple colors from multiple angles, highlighting level details of product surface

Can be applied to inspecting missing/wrong/inclined parts, insufficient/excessive/no soldering, and other defects in PCB industry.

Using LED Driver can adjust the RGBW lights intensity individually (mixing colors possible) and can apply strobe control.

Spot Lights

Spotlights are used in applications that require intense illumination of a limited area.

Back Lights

The backlight is a high intensity, uniform and collimated illumination that produces a very uniform surface light emission profile. It generates dark object contrast against a bright background, highlighting the object’s shape and outline distinctly. This lighting type is used to detect the presence/absence of holes or gaps, measurement, or verification of the target outline shape, as well as enhancing cracks, bubbles, and scratches on clear target parts.

Lighting Technique: Using Polarizing Filters

The polarizing filters are using to reduce unwanted glare that is coming from shine surface of objects .

Lighting controllers for machine vision

Illumination is a critical component of machine vision systems because it determines how the object being imaged appears to the camera. LEDs are the most widely used illumination source, and while factors such as the direction, wavelength and intensity of illumination all have a key role to play, precise control of the lighting can be crucial. Dedicated lighting controllers offer a number of benefits including maintaining consistent light levels, pulsing lights for high-speed imaging, overdriving LEDs for enhanced intensity output and the establishment of sophisticated lighting sequences.

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