3D scanning

What is 3d scanning?

the process of analysing and understanding objects, the scanners are able to get an accurate reading of the objects that are being scanned. This then allows the user to put the 3d model into software and create other components that interact with the 3d scan with high precision.

what is CMM?

A contact coordinate measuring machine, uses a probe which comes into contact with the object which creates a digital version of the object.

 

optical range scanning methods

Advantages:

– non contact, safe, inexpensive and fast

disadvantages:

– sensitive to transparency, confused by specularity, texture suffers

 

Non contact passive scanning:

Passive 3D imaging solutions do not emit any kind of radiation themselves, but instead rely on detecting reflected ambient radiation. Most solutions of this type detect visible light because it is a readily available ambient radiation.

 

stereo scanning methods

advantages:

– passive, cheap, easy to accommodate motion, intuitive analogue to human vision

disadvantages:

– only acquire good data at features, noisy data, bad with silhouettes, confused by non diffuse surfaces

 

Shape from motion:

Advantages:

– feature tracking easier than correspondence in far away views, mathematically more stable

Disadvantages:

– does not accommodate object motion, still problems in areas of low texture in non diffuse regions and around silhouettes

TOF scanner:

The time-of-flight 3D laser scanner is an active scanner that uses laser light to probe the subject. At the heart of this type of scanner is a time-of-flight laser range finder. The laser range finder finds the distance of a surface by timing the round-trip time of a pulse of light. A laser is used to emit a pulse of light and the amount of time before the reflected light is seen by a detector is measured.

Pulsed time of flight – often used for scanning but,dings, rooms and archeological sites.

advantages:

– large working volume

disadvantages:

– accuracy is weak, need to time to 30 picoseconds, doesn’t scale with working volume

 

During the lecture we first learnt all about the different types of 3d scanning and were shown the advantages and disadvantages of each method. After this we had tutorials which took place in the heavy engineering building. During these we were shown 2 different types of scanners and what they are typically used for. After we had been briefed on the scanners we were shown the software in which the scanners send the data to.