Our wikipedia, marking methods: 3D internal engraving

Internal laser engraving involves creating graphics (as well as texts) inside a glass or crystal element. The engraving made in this way is white in color and slightly transparent.

The technology of internal engraving involves focusing a laser beam at a specific point inside a glass. The high power released at the point of focus causes microcracks in the material. Such a point is a kind of pixel, from which we build an image. We regulate the brightness of a given area of the graphics by the density of the points and the number of layers.

The limitation of laser engraving is the shape of the glass statuette. Due to the very precise optics of the engraving equipment, the surface through which the engraving is performed must be perfectly flat and smooth. Any scratch or unevenness on the glass surface can disturb the laser beam and damage the final image on the glass.

Internal 3D engraving is a process of laser engraving a 3D object inside a piece of glass.
Unlike 2D engraving, we are not limited to just one plane in 3D internal engraving. We can engrave almost the entire available volume of the figurine.
The points that make up the image are arranged in space so that the resulting 3D graphics can be viewed from any side of the figurine.
The 3D internal engraving method allows for the engraving of complex objects, including their interiors.
This type of engraving is used for three-dimensional objects, mainly made of optical glass (crystal). It is very rarely used for flat figurines due to their too small thickness.