Having worked in the vision measurement industry for over two decades, I’ve seen many customers struggle when it comes to measuring highly reflective materials. Parts such as chrome-plated components, polished stainless steel, and mirror-finished aluminum may look flawless to the naked eye, but under a vision measuring system, they often become the toughest challenge.

Many customers, when first attempting to measure such parts, notice large light spots on the image, making true edges nearly impossible to distinguish. Others report that repeated measurements at the same location yield inconsistent results, with poor repeatability. This issue is especially common in automotive components, polished molds, and decorative parts.

The root cause is quite clear. Vision measurement relies on diffuse reflection from the workpiece surface to form stable grayscale edges. However, highly reflective surfaces behave more like mirrors: incident light follows the law of reflection, with most of it bouncing away at fixed angles. As a result, the camera doesn’t receive a smooth grayscale transition but rather overexposed regions. True edges are often “washed out,” or false edges appear, which misleads the software.

One of my clients encountered this when inspecting chrome-plated automotive trims. Measuring the same position three times produced results that differed by tens of microns. Initially, they suspected a lack of equipment accuracy. After analyzing the images together, we found that the strong reflected light had obscured the edge, and the software was detecting different edge points each time. Left unresolved, this not only prevents accurate measurements but also risks misjudging entire production batches.

Based on my experience, I usually suggest the following countermeasures:

1. Adjust the lighting. Highly reflective parts are most sensitive to single-direction illumination. Coaxial lighting is often effective, as it directs light to and from the lens along the same axis, minimizing harsh reflections. For stainless steel surfaces, adding a polarizer can also help suppress glare. Modern vision measuring machines often come with controllable segmented ring lights that allow multi-angle illumination, enabling operators to select the clearest image—very practical for chrome parts.

2. Temporary surface treatment. With customer approval, a matte developer spray can be applied to the surface, turning mirror-like reflection into diffuse reflection. For example, one mold-making customer had polished parts that were almost impossible to measure. After applying the spray, edges became clear and results stabilized significantly. For thin sheet parts, attaching a frosted film can also improve imaging. Of course, such methods add an extra step, so they must be balanced with process requirements.

3. Optimize software and algorithms. Hardware alone can’t always solve the problem—software processing plays a crucial role. Multi-threshold fitting and glare filtering can exclude overexposed pixels, improving edge detection accuracy. Sub-pixel fitting techniques are also valuable, as they can enhance repeatability even when edges are slightly blurred.

Additionally, I often remind customers to check the environment and fixturing. Sometimes the issue isn’t with the equipment itself, but with excessive ambient light or unstable clamping that alters the reflection angle. When conditions aren’t consistent, image results will inevitably vary.

In summary, while highly reflective materials present a clear challenge in vision measurement, they are far from unsolvable. By understanding their optical properties and combining lighting adjustments, surface treatments, and algorithm optimization, suitable solutions can be found in most cases. In my twenty-plus years of experience, I’ve learned that solving measurement problems isn’t only about the machine—it’s about understanding material behavior and responding flexibly on-site.