where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -

Articles & News
NDT Inspector,
Iran, Joined Mar 2013, 93


NDT Inspector,
Joined Mar 2013
08:24 Jan-03-2015
Photoelastic Visualisation of Phased Array Sound Fields: Part 19 – Formation of grating lobes

Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1254

Ed Ginzel

R & D, -
Materials Research Institute,
Joined Nov 1998
19:40 Jan-03-2015
Re: Photoelastic Visualisation of Phased Array Sound Fields: Part 19 – Formation of grating lobes
In Reply to Ali at 08:24 Jan-03-2015 (Opening).

An explanation of grating lobes is presented in the Jan 2015 edition of NDT.net.
Several people deserve special thanks. First I would like to thank Rolf Diederichs for publishing the material. By means of the combined formats of written word and video imaging, Rolf has managed to make the NDT.net noticeably superior to the traditional hard-copy journals available to readers.
The idea to produce an explanation of grating lobes is thanks to Ali Golshani. Ali asked me if it would be possible to see grating lobes using photoelastic visualisation. For many years, PAUT instructors have simply stated the sort of explanation provided in the official definitions, i.e. "parasitic replications of the main beam caused by spatial under sampling (pitch between elements compared to wavelength)". This has not been very helpful for students to understand their origin. At the time Ali asked me I was not sure it could be done...I hope the explanation has met his expectations.
As with so many of my projects, I again resorted to Civa to help with my explanation and personal understanding of acoustic phenomena. Using Civa, I was able to configure a delay law that would produce a pronounced grating lobe with the limited selection of phased-array probes I have. I would like to thank the good people of the CEA and EXTENDE for their ongoing help with my use of Civa.
Finally, the video of a simple 74° beam in transverse mode is in itself not a great illustration of the lobes that form. In order to illustrate how constructive interference causes the lobes I used a technique of image addition first developed by Dr. Till Schmitte. I would like to thank Till for pointing out this very useful tool of image processing.


Product Spotlight


Scalable small footprint X-ray inspection systems for assembly and laboratory applications. The
YXLON Cougar EVO series was designed to provide the "best-in- class" inspection solutions for SMT, semiconductor, and laboratory assembly applications, while maintaining a small system footprint for maximum convenience. With optimized software and hardware, these systems produce higher quality and more consistent results than other electronics inspection systems currently on the market.

Semi-Automated Phased Array Immersion System for Small Composite Parts

Turn-key semi-automated system as an improved and affordable solution for inspection of small comp
osite parts. Includes support table, immersion tank, scanner, PA instrument, PC, Analysis software, database, wedge management and other options.

SONOAIR - air-coupled Phased Array Ultrasonic Inspection System

For highly attenuating materials, the performance of the system is critical. The ultrasonic sensors,
the scanning area and the system settings should be flexibly adapted to the test task and the material. These high expectations are met with the new and modular testing system SONOAIR. With the world’s first air-coupled phased-array UT inspection system SONOAIR we developed a technology that works with up to 4 transmitter and receiver channels with freely configurable square wave burst transmitters as wells as low noise receiving amplifiers.


Teledyne ICM’s CPSERIES has been designed with a view to revolutionizing the handling and perfor
mances of portable X-Ray sets. Despite having managed to halve the weight of similar portable X-Ray generators available on the market (while continuing to provide the same power output), the SITEX CPSERIES generators feature a shutter, a laser pointer, a beryllium window, an aluminum filter and two integrated diaphragms (customized sizes are available upon request). Without compromising the robustness and reliability for which ICM products are renowned, the small size and light weight of the SITEX CPSERIES will radically change the way that you perform your RT inspections. And you will see a positive impact in terms of both quality and return on investment (ROI).

We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
this is debug window