Why use a polarizing LED ring light for electronics inspection

The benefits of using a polarizing LED ring light for electronics inspection

If you spend any time inspecting metallic parts or circuit boards under a stereo inspection microscope, you’ll be familiar with the persistent challenge of glare and excessive reflection.

Glare can easily obscure defects or structural detail – and in electronics, the slightest defect may ruin your whole inspection process.

Fortunately, Polarizing LED ring lights provide a relatively cheap and easy solution to the problem of glare from metallic samples (PCBs, bare solder boards, connectors or copper parts).

By replacing your standard PCB inspection microscope illumination system with a Polarizing LED ring light, you can drastically reduce the effect of glare and achieve crisp images with great contrast. Thus making it a worthwhile upgrade if you are doing PCB inspections under the microscope.

Without Polarizer

With Polarizer

What is polarized light?

A regular light microscope uses unpolarized white light. This is the type of light that we see, and its waves vibrate in random directions.

A polarizer is a special filter that only allows light vibrating in a specific orientation to pass through. Light that only vibrates in a specific plane is known as polarized light.

Polarizing microscopy involves the use of polarized light to investigate the optical properties of various specimens. Although originally used mainly in the field of geology, it has recently become more widely used in industrial inspection, medical and biological research fields too.

Without Polarizer

With Polarizer

How the Polarizing LED ring works

The polarizing LED ring uses two separate polarizing filters to give you greater control over the light hitting your sample. One filter is set up in front of your lens, while the other (the adjustable) filter sits in front of your lighting array.

A single polarizer reduces glare on its own but using two allows you to find the setting that provides maximum contrast while minimising glare.

Polarizing filters do not necessarily get rid of all the glare that remains under a standard LED ring light, but they do give you a qualitatively different view of electronic hardware.

Without Polarizer

With Polarizer

Is it worth getting a polarizer? 

A casual user might find the $500 setup cost of basic polarizers prohibitive.

But in an industry where quality is critical (biomedical, electronic manufacturing or industrial machining), it is absolutely worthwhile. For a relatively low cost you get a huge increase in visual clarity.

The clearer images help you (as the operator) to detect defects faster and work more efficiently. And the improved imaging allows you to work in a more relaxed and comfortable way, which can lead to an increase in productivity.

Can I upgrade my current microscope?

While some microscopes come with a polarizing system built-in, it’s easy (not to mention cheaper) to modify your existing microscope with a polarizing LED ringlight.

Setup takes a few minutes. First, position one polarizer inside the centre of the light ring. Second, screw the second polarizer onto the outside. Third, attach the ring to your microscope. And you’re away …

Dino-Lite AM73915MZTL Polarizing Digital Microscope

Another microscope to consider with polarizing light capability is one of the Dino-Lite digital microscopes such as the Dino-Lite AM73915MZTL with long working distance focusing making it beneficial to electronics inspections.

The Dino-Lite with polarizer have both adjustable and a fixed polarizers. The adjustable polarizer, polarizes the microscope light source and the fixed polarizer, polarizes the light between your specimen and the cameras imaging sensor. The degree of polarization can be adjusted by rotating the wheel of the adjustable knurled rubber ring.

Dino-Lite AM73915MZTL with long working distance

Polarizer function demonstrated with Dino-Lite Digital microscope

Dino-Lite with stand

What to look for in a Polarized LED ring light

Although all polarized microscopes have the same fundamental objective, they are available in a wide range of designs and configurations from the top makers. As a guide, you can compare the following features of Optico’s 8W-LED microscope ring light with polarizer with any quality product you may be considering for your needs.

  • 8 x 1 watt high-quality LED light
  • adjustable brightness intensity
  • rotatable analyzer 360º
  • polarizer drops into slot and is removable
  • 62mm image digitisation (ID) – works with most stereo microscopes
  • UV-free
  • electrostatic discharge (ESD) safe
  • restriction of Hazardous Substances (RoHS) compliant
  • angled lighting for even illumination of LEDs
  • optional polarizer available
  • lamp life 6,000 hours – 6,000k to 7,000k cool white light.

For simple and effective manual visual inspection, you can’t go past a polarizing light accessory for your microscope.

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