A couple of weeks ago, we introduced our 3D scanning project, Stamp printing plates, dies and rollers: from vault to view, in partnership with UCL. Mona Hess, Research Associate and PhD candidate at UCL, is the 3D specialist for this project. Mona has been working with museums for the past 10 years, creating three-dimensional digital models and physical replicas through 3D printing (such as these busts of Darwin and James Watt). She is interested in opening up archives and collections, giving visitors access to hidden objects. In this post she will introduce the different techniques we will be using to capture some of our hard-to-photograph philatelic material.
The BPMA’s philatelic collection goes far beyond stamps. It also includes plates, stamps and rollers, all of which are difficult to photograph. Many of these objects, especially the plates, rollers and dies can’t be on display to the public. There are conservation and security issues that prevent them from coming outside of the vaults. Despite this we still want philatelists, researchers, enthusiasts and visitors to be able to see and interact with these objects digitally.
The creation of these 3D digital objects can be produced by ‘3D imaging’. We will be using “non-contact optical surface imaging”. The surface of the object will be recorded from all angles, and the model can be turned, zoomed and panned, almost as if you would have the real object in your hand.
For creating three dimensional images of printing plates, dies and rollers we will apply and combine different technologies:
- Photogrammetry and ‘structure from motion’ is based on photography. We will produce a set of images while walking around the object. Usually the camera settings, background and lighting does not change while we do that. A software programme is then able to compute the common points to create a three-dimensional surface of the object with the colour, called ‘texture’. To be able to apply a scale to the object we need to include some known lengths in the photographs. This method is versatile with regards to object type imaged the equipment is very mobile, and the equipment affordable.
- For Reflection Transformation Imaging (RTI), we place an object under a dome at UCL with a number of lights around and a camera looking into the dome from the top. We can now view the object with ‘digital re-lighting’ and guide the light over the object with a virtual torch.
- Low cost 3D laser scanning can use sensors usually intended for gaming, like the Xbox Kinect. These sensors have inbuilt range sensing with human gesture recognition (natural user interfaces) that allow for objects to be captured using infrared signals. From initial tests we know that this technique is able to record the shiny surfaces of the printing plates. The information will give an overall picture, but not enough detailed information of the surface.
- Therefore we will also use High resolution 3D colour laser scanning on selected objects. The Arius 3D colour laser scanner is installed fixed in an air-conditioned room and used for high-quality digitisation of museum objects. While this will give us a very detailed surface geometry, all objects will need to come to UCL.
As you might have gathered, the printing plates, dies and rollers will be difficult objects, so multiple techniques may be enlisted for each object. We will have to combine recording methods to find out how we can represent the fine engraving used in the dies and the overall geometry of the plates.
We would like to invite you at the end of the project to get your hands on the digital 3D models and tell us what you think about them. It is important for us to know how detailed these objects should be and depending on how you want to use them (i.e. on your mobile phone) the resolution can be lower.
If you are interested to know more about the technology, please visit Science of 3D where we explain the science behind our optical 3D imaging.
Stay in touch with me by following @Mona3Dimaging .
-Mona Hess, UCL
For the time being, we would love to hear your thoughts on this project. How would you use these 3D objects? Would you like to see them in an exhibition? We look forward to hearing what you have to say!