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Technical Discussions
Rolf Diederichs
Director,
NDT.net, Germany, Joined Nov 1998, 608

Rolf Diederichs

Director,
NDT.net,
Germany,
Joined Nov 1998
608
08:37 Apr-16-2002
Holography vs Shearography

Holography and Shearography are similar techniques. Holography
employs interferometry by using two beams of laser light.
Shearography on the other hand, employs a single beam of laser
light which is reflected off the specimen.

What are the pro an cons of these techniques?
Do they have different defect detection capabilities?
What is more widely applied?

I have read that shearography is much less sensitive to external
vibration interference and hence much more suitable for
production and field environments.

Rolf Diederichs


    
 
 Reply 
 
Jörg Collrep
Jörg Collrep
09:53 Apr-17-2002
Re: Holography vs Shearography
The advantages of shearography to many other techniques are:
- low sensitivity against external vibrations
- fast detection of defects ( within a few seconds )
- user friendly and easy to handle
- fully industrialised on Car, Truck and AC tire inspection systems
- fully automised test procedure
- automatic fault detection based on customer data available
- pure quality information
- full field measurement
- low requirements on user skills
Holography advantage
- static and dynamic excitations
- detailed and quantified informations
- strain & stress measurement interface available
- vibration measurement

Both techniques have a wide range of applications, but shearography is already approved at a harsh environment.

Jörg Collrep


: Holography and Shearography are similar techniques. Holography
: employs interferometry by using two beams of laser light.
: Shearography on the other hand, employs a single beam of laser
: light which is reflected off the specimen.
.
: What are the pro an cons of these techniques?
: Do they have different defect detection capabilities?
: What is more widely applied?
.
: I have read that shearography is much less sensitive to external
: vibration interference and hence much more suitable for
: production and field environments.
.
: Rolf Diederichs
.



    
 
 Reply 
 
Anand Asundi
R & D, -
Nanyang Technological University, Singapore, Joined Feb 2001, 10

Anand Asundi

R & D, -
Nanyang Technological University,
Singapore,
Joined Feb 2001
10
02:00 Apr-22-2002
Re: Holography vs Shearography

Shearography is the preferred choice for industrial applications of relatively large objects due to its vibration insensitivity. The technique is primarily used for qualtitative interpretation.

Holography would be preferred for smaller objects and as Gabor had initially proposed for microscopic imaging. Recently with the advent of digital holographic interferometry, quantitative measurement become possible without any phase shifting.

Digital holography can take different forms:
Optical recording - digital reconstruction: This is ideally suited for deformation measurement of small objects.

Digital Recording - Optical reconstruction: Computer Generated Holograms (CGH) used primarily as Holographic Optical Elements (HOE). Using a LCD based projector, CGH animations can be readily displayed. Possible alternate to laser shows using scanners.

Anand Asundi



    
 
 Reply 
 

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