Polarized Light to the Rescue

In industrial inspection and precision machining, this problem often causes data errors or blind spots.Using polarized light, the system can adjust the angle of the light source and the angle of the polarizing filter to reduce glare, thereby improving the accuracy of the inspection.These are suitable for mechanical processing, electronic component testing and other scenarios, and are simple to operate with controllable costs.

Why does deep-hole reflection give people headaches?

When there is a deep hole structure, such as on the inner wall of a part or inside a tube, a regular light source can easily produce a glare, making it difficult for the camera or the naked eye to see the details.In particular, in the industrial quality inspection stage, reflection can cover up defects such as cracks and burrs, directly affecting the product's pass rate.At this time, increasing the brightness of the light actually makes the problem worse--the glare becomes more intense, and the details become even more blurred.

The core principle of polarized light.

The key to polarized light technology is controlling the direction of light wave vibrations to reduce reflection interference.In short, it's like putting on a pair of polarized sunglasses for the light source and the camera lens, allowing only light from a certain angle to pass through and filtering out scattered reflections.

Tools: Don't worry, the costs are low.

You don't need to buy expensive equipment. Just a set of linear polarizers and an LED light source with an adjustable angle is enough.Polarizing filters are placed on the lens and the light source. Then the two filters are rotated manually until the reflections on the screen are greatly reduced.In an industrial application, a camera with built-in polarization capability can be used.

How to do it: Two steps to remove glare.

First the position of the light source is fixed, and the light is allowed to strike at an angle of 30-45 °, which reduces glare.Next, rotate the polarizer in front of the camera and observe the real-time image to find the point of minimum reflection.If the effect is not sufficient, the direction of the polarized light can be adjusted until the texture becomes clearly visible.

Small experiences in practical application.

When shooting metallic objects with strong reflections, it is recommended to use a soft reflector in conjunction with the flash.A half-transparent acrylic plate placed over the hole will make the light more uniform.An old-timer from a machine shop once shared a tip with me. When checking threaded holes, they would use a cotton swab to apply a little talcum powder to the inside walls, which reduced glare without the need for a polarizing filter. Of course, this is only appropriate in cases where a little contact is permitted.

Common pitfalls.

Don't assume that the more expensive the polarizer, the better. Experiments showed that there was less than a 10 % difference between the performance of a US $ 3.50 polarizer and a US $ 35 one in most deep hole situations.The most important point is the matching of the light source angle and polarization direction.If the surrounding light is too strong, remember to put on a light shield, or else the outside light will interfere with the polarization effect.