In stabilized on a plane surface, a

In measuring the 3D objects
we can find many types of equipment that can be used to measuring
them. 3D scanners can be classified
in two types of equipment which are contact and non-contact 3D scanners.
For non-contact, it is divided
into 2 categories, active and passive.

There are variety
technologies for digital acquisition 3D object shapes and each of them are working
differently and has its own specifications. These are the description of each technology and will help us understand   more:

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Contact

 

Contact 3D scanners explore the physical objects while in contact with the objects.
It scans the precision plane surface,
ground and polished to a specific
maximum of surface roughness. However, if the object
is not flat or cannot stabilized on a plane surface,
a fixture  is used to
support and held it in plane.

A CMM (Coordinate Measuring
Machine) is an example of the contact measurement system.
It is very precise
and mostly being used in
manufacturing. However, there are some disadvantages of CMMs which are they require contact
with the object
being scanned and by scanning
the object might modify of damage it. It also very significant when scanning the valuable object such as historical artifacts. Besides,
CMMs are relatively slow compared to other scanning methods and the fastest of CMM can run at a few hundred hertz only. In order for CMMs to perform as indicated, these machines need to be isolated
from the changes such as vibrations, part displacement and temperature variations.

 

 

Non-contact

·        
Passive

Passive
scanners do not emit radiation
and they only rely on detecting reflected ambient radiation. Most of these
type of scanners detect visible light as it

is found in the ambient radiation
and these passive methods generally inexpensive because
they do not required any particular equipment and use digital camera only. In addition,  the passive methods provide low accuracy.

 

 

·        
Active

 

Active scanners
emit some kind of radiation such as X-ray
and ultrasound

or light in order to probe and object or environment and detect the reflection or radiation passing through
object. To record the surface distance,
the light or radiation emitted by scanner
is reflected by the object scanned and sends back the information to the scanner. However, it also has the disadvantage which is this type of scanners has limitations and has difficulty scanning re flective
or transparent objects.

 

 

 

 

 

 

i.                         
Time-of-flight

 

It uses a laser light to probe the object. It is equipped
with a time- of- flight laser rangefinder to find the distance of a surface
by timing the round-trip
time of a pulse of light. Before the detector sees the reflected light,
 the laser emits a pulse of light  and the amount of time is measured.

 

ii.                           
Triangula
tio n

 

In triangulation, it uses laser light to probe the environment. It shines a laser on the subject then uses a camera to look for the location
of the laser dot which appears
a different places in the camera field view. It depending on how far away the laser strikes a surface.
This technique consist
the laser dot, the camera and laser emitter form a triangle and because of that, it is called triangulation.

iii.                            
Structure
Light

 

Structure Light 3D Scanner project a light pattern
on
the subject. It has two main benefits. There are it is uses to capture speed and precision and it also can scan the entire field of view and generate
exponentially more precise
profiles than laser triangulation. Instead of scanning
one point at a time, they can scan multiple
points or the entire field of view at once.

 

iv.                          
Modulated
Light

 

Modulated Light 3D Scanner can project a continual
changing light on the subject.
It creates a set of linear
patterns on object then a camera detects
the reflected light and determines the distance the light traveled and shifting each line on the pattern. In addition,
the scanner of modulated light can ignore the light sources from other than laser so there is no interference
 will occur.

 

 

v.                         
Handheld
Laser Scanner

 

Handheld Laser 3D Scanner create a 3D image using the triangulation mechanism.
By using the reference features of scanned surface, it can determine
 the object position.

 

vi.                          
Handyscan
3D by Creaform

 

For Handyscan 3D Scanner by Creaform,
it is a portable and versatile self-positioning 3D scanner.
It uses Creaform positioning targets
to reference its position
from the object to scan.