Inside glass engraving
A glass engraving , and laser engraving or Vitrography called, is a method of displaying images of three-dimensional body within a transparent called solid, often 3D laser crystal. In addition to glass , other materials such as sapphire , diamond , PMMA and polycarbonate can also be internally engraved.
In contrast to conventional, classic photography , in which a two-dimensional image of an object, a person or a scene is displayed on photo paper , for example , the 3D photo is z. B. is shown in a glass block and can be viewed from all sides like the object or the person himself.
admission
Portraits can be taken, for example, with a 3D scanner, which records a person's face according to the principle of strip projection. The data obtained from the three-dimensional image are converted into a point cloud using software . The file contains every single point of the portrait arranged within a three-dimensional space. Each of these points is provided with the three-dimensional coordinates X, Y and Z.
A 3D model can also be calculated from different 2D photos with different perspectives, e.g. B. for sights that are too big for a scanner.
engraving
To generate an image point , a laser beam (or bundle of rays) is deflected by means of a scanner over two mirrors operated by galvanometers on the X and Y axes and focused with a lens into the interior of the glass body. In the focus , the spatial and temporal energy density of the pulsed laser beam is so high that the glass is thermally destroyed at one point by ionization and the formation of plasma (crack formation, melting and evaporation), while the still wide beam in front of and behind neither the two glass surfaces nor causes damage to the focusing lens. The small dots that are a few µm ( micrometers ) in size are visible as white dots in daylight due to the refraction and scattering of light .
Three mechanical axes of movement, whereby either the object or the laser head with scanner is moved, enable the points to be arranged at any coordinates in the glass block. The arrangement of many points creates two or three-dimensional markings in the glass.
A pulsed Nd: YAG laser with a wavelength of 1064 nm or ( doubled in frequency ) of 532 nm is used for engraving inside the glass . With pulse repetition frequencies between 500 Hz and 3 kHz, 500 to 3000 points per second can theoretically be generated inside the glass.
The glass must have a smooth and polished surface so that the laser beam can penetrate the inside of the transparent material unhindered. Otherwise the beam would be diffusely reflected or deflected by the non-transparent surface of the glass .
The process of scanning and laser cutting a 3D portrait into a glass block with dimensions of 50 × 50 × 80 mm and a number of points of around 180,000 to 350,000 points for a standard 3D portrait photo takes around 3–5 minutes.
Color representation
Vitrography creates small structures in the glass, the amorphous glass is crystallized and visible as white dots in very small dots of a few µm in daylight due to the refraction of light. Differences in brightness are created by the distance between points: Many points very close together appear as a white area, a few points with a slightly larger distance appear as a gray area. The 3D portrait in glass appears to be a black and white photo. A colored laser engraving is currently not possible. The white laser points can only be illuminated in color by LED lighting, which can be used to create a color effect.
Application examples
The inside glass engraving offers a high level of resistance to influences on the surface or from outside due to the fact that the surface is not damaged and the position of the engraving inside. Dirt and other damage (e.g. graffiti or scratches) do not destroy or damage the engraving.
- Glass blocks are known as promotional gifts with three-dimensional product images or company logos inside, souvenirs (e.g. 3D Eiffel Tower in a glass block). Another application is the marking and labeling of products made of glass to protect against counterfeiting (e.g. medicine bottles). Photos (rasterized images) or 3D portraits in glass can also be created.
- The technique of engraving on the inside of the glass has also already been used for the implementation of permanent and environmentally resistant art objects, such as Basic Law 49 by the Israeli artist Dani Karavan .
history
Around 1971, Russian physicists lasered the first three-dimensional structures for the first time at speeds of one point per second (corresponds to 1 Hertz). Russian and Chinese laser manufacturers offered lasers with pulse repetition frequencies around 30 Hertz until the end of the 1990s . In 1997 the Fraunhofer Institute for Material and Beam Technology succeeded in using scanner technology to implement a pulse repetition frequency of 500 Hz, which made commercial use possible. The process was made ready for production in 1998 by Vitro Laser GmbH based in Minden in cooperation with the Fraunhofer Institute for Laser Technology (ILT) in Aachen. At the Hanover Fair 1999, a face scan was generated using a 3D scanner, which was then engraved into a glass block. Today there are numerous suppliers of 3D portrait engravings in glass worldwide.
Web links
Individual evidence
- ↑ Source: LOOXIS