Extract "Color" and "Shape" Separately from a Single Capture: Observing an Enamel Pin in 3D with FORESIGHT STEREO

To the human eye, the "color" and "shape (relief)" of a product surface look mixed together. That is exactly why it is hard to tell color unevenness from a real scratch, or a pattern from an engraving. In this post, we photographed one enamel pin badge with our stereo 3D imaging technology FORESIGHT STEREO and present the results of taking four types of output from that single capture at the same time. Follow the four images in order to see how, once the color is peeled away, only the shape remains.

LIVE image of an enamel pin badge captured with FORESIGHT STEREO. The orange sun face and blue ring appear in full color

Why observe an enamel pin?

The subject we chose is a commercially available enamel pin badge with a sun face bordered by the words "EVERYBODY LOVES · THE SUNSHINE." From an inspection-technology standpoint, it conveniently combines two elements on the same surface.

• Enamel color graphics: "color information" sitting on a flat surface, such as the orange face, the blue ring, and the lettering colors
• Raised metal lines: "shape information" where the surface itself is raised, such as the metal outlines separating letters and patterns, the outer rim, and the radiating notches of the sun

Moreover, enamel and metal are glossy materials that reflect light strongly. With an ordinary camera, reflection and shading mix, making it hard to tell shades of color from real relief. In other words, this pin is a sample that concentrates the hardest part of inspection: "color and shape are mixed, and the reflection is strong."

What is FORESIGHT STEREO? Four outputs in one shot

FORESIGHT STEREO is TOMOMI RESEARCH's stereo 3D imaging technology. Its key feature is that it generates four types of output simultaneously from a single capture.

1. LIVE image: the appearance just as the human eye sees it
2. 2D Texture: a layer that extracts only the surface's "color and pattern"
3. 3D Surface: a layer that reconstructs only the surface's "shape (relief)"
4. Surface Normal: intermediate data that encodes the surface's "orientation"

Rather than recapturing or adding separate processes, a single shot lets you lay out the "color layer" and the "shape layer" side by side. This simultaneity translates directly into throughput on the inspection floor. Now let us look at the four outputs in order.

(1) LIVE image: the "starting point," with color and shape mixed

First is the LIVE image, the state as seen by the human eye (the image at the top).

A vivid orange sun face, a deep blue ring, the luster of metal and the gloss of enamel. The letters and patterns are clearly visible, but here "color" and "shape" are melted together in a single picture. Are the letters on the blue ring simply painted in a different color, or are they separated by metal steps? The human eye cannot tell. This "mixed state" is the starting point that we will now separate.

(2) 2D Texture: keeping only color (albedo)

Next is the 2D Texture, a layer that extracts only color.

2D Texture output of FORESIGHT STEREO. A grayscale image with shading removed, extracting only color and pattern (albedo)

Shading and highlights from the illumination have been removed, and the letters and patterns can now be read at a flat, uniform brightness. What is being extracted here is technically called albedo (the color and reflectance inherent to the material itself), in other words "the base color and pattern of the material, undisturbed by illumination or the shadows of relief."

• What it keeps: surface design information such as letters, patterns, and color separations
• What it discards: shadows and highlights created by relief

Because patterns alone can be evaluated without being misled by the shadows of relief, it is well suited to examining "color-side" defects such as print misregistration, color unevenness, fading, and missing print.

(3) 3D Surface: discarding color, keeping only shape (the highlight of this article)

And now the star of this post, the 3D Surface.

3D Surface reconstructed with FORESIGHT STEREO. Color disappears, and only relief such as the raised metal lines and the steps of the enamel emerges

All the color has vanished, and only the relief emerges, like a relief carving.

• Steps between enamel and metal: the raised metal lines surrounding the letters and the steps at the boundary between the ring and the sun rise as smooth undulations.
• Radiating notches of the sun: the fine serrations around the sun can be read three-dimensionally, with their shadows.
• Relief of the face: even the slight swelling of the eyes, nose, and mouth remains as shape.

What is happening here is that "color that merely sits on a flat surface disappears, because it does not exist as shape." Neither the color of the blue ring nor the color of the orange face appears in the 3D Surface. Only the areas where the surface is physically deformed remain. In other words, FORESIGHT STEREO removes "what color sits on top" and extracts purely "what shape it has." This is a viewpoint for examining shape-side defects such as chipped metal lines, burrs, dents, and bubbles.

(4) Surface Normal: expressing the "orientation" of the surface as color

Finally, the Surface Normal, the intermediate data from which the 3D Surface was reconstructed.

Surface Normal output of FORESIGHT STEREO. A normal map encoding the surface orientation of each pixel as color

It is a distinctive map that looks as if the whole image is glowing in blue tones. This is the surface normal (the direction in which the surface at each pixel faces) encoded as color. A "normal" is like an arrow showing which way the surface at that point faces, and the color changes sharply where the slope of the surface changes, that is, at edges and where relief rises.

In fact, in this image, the "lines where the surface slope switches," such as the edges of the letters, the sun's radiating lines, and the outline of the face, appear distinctly. Because it is highly sensitive to minute relief and rising edges, it not only serves as the foundation for 3D Surface reconstruction but also functions as raw data for reading clues to slight steps and fine scratches.

What it means on the inspection floor: separating "color or shape"

Looking at the four outputs side by side, the value FORESIGHT STEREO brings to the floor becomes clear.

• Separating color unevenness from scratches: by looking at the 2D Texture (color) and the 3D Surface (shape) separately, you can tell whether something is "color unevenness (a texture defect)" or "a scratch or dent (a shape defect)."
• Strong on glossy and reflective materials: even with materials like metal and enamel, which reflect strongly and whose scratches get lost in the light with an ordinary camera, relief can be captured as shape.
• Reading engravings and embossing: engravings, raised features, and fine relief beneath printing or paint can be read without being misled by color.
• Complete in one shot: the four viewpoints are obtained at the same time in a single capture instead of being recaptured separately, so inspection throughput is not reduced.

Note that this is only an observation demo on a single sample and does not guarantee performance for every material and every defect. Even so, the four images speak eloquently to how the idea of "looking at color and shape separately" could change inspection.

Summary

• FORESIGHT STEREO is a stereo 3D imaging technology that generates four outputs simultaneously from a single capture: LIVE image, 2D Texture (color), 3D Surface (shape), and Surface Normal (orientation).
• On the enamel pin, only color remained in the 2D Texture, while in the 3D Surface the color disappeared and only the relief emerged. "Color" and "shape," which mix for the human eye, can be separated into different layers.
• Being able to separate color and shape connects directly to on-site challenges such as separating color unevenness from scratches, inspecting glossy materials, and reading engravings.

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Would you like to try FORESIGHT STEREO on your own difficult samples (glossy or reflective materials, or workpieces where color and relief are mixed)? We welcome inquiries about demos and sample evaluations. Please feel free to contact us.

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