Image Processing

Research Relevance

The research and development of the team follows closely the increasing industrial needs for automatic 3D inspection and measurements, particularly with wide adoption of 3D additive manufacturing.

  • In aerospace industry, one of the most important needs is the faster yet more accurate disposition of manufactured and used parts. By doing so, industry can improve their capabilities to work on various components, reduce cycle-time and costs. Addressing the need would impact Singapore economy in terms of creating more MRO activities in Singapore. The industry need requires automated inspection and measurement of the dimensions of polishing surfaces, the dimensions of parts to be repaired or remanufactured, and the defects in composite structures. Also it requires failure analysis and prognosis of structure integrity and remanufactured components and systems.
  • In oil & gas sectors, one promising application identified by an industry initiative in SIMTech is Gun-drilling. There is total lack of practical instrumentation and techniques to regrind and measure the apex, edge radius and Ra of the drill bits. The development of the measurement technologies would bring the impact to local economy in terms of retaining O&G MNC into Singapore and developing a cloud of SMEs for the high-value added manufacturing in gun-drilling area.

Research Focus

  • High energy X-ray CT system by using dual X-ray sources (225 kV & 450 kV) to reconstruct 3D internal structure of objects up to 0.5mx0.5mx0.5m in size and 50kg in weight. The maximum penetration length is equivalent to 70mm steel or 250mm aluminium;
  • 3D image processing for 3D CT data visualization, volumetric registration and segmentation, CT internal defect inspection and dimension measurement;
  • High speed image processing by exploring line-scan imaging techniques and computing power of GPU and FPGA.

Research Staff
Dr Malcolm Andrew Alexander
Dr Yin Xiaoming
Dr Liu Tong
Dr Liu Wei
Ms Zhao Li
Mr Jiang Ting Ying
Mr Liu Tieping
Dr Xu Jian (Team Leader)

High energy X-ray CT system
Micro-CT system
High speed large field of view vision inspection platform


Automatic 3D inspection and measurements is approached from three areas, X-ray CT, 3D image processing, and high speed image processing. The key challenges are the imaging and image processing resolution and the uncertainty management for measurements. 

In the area of X-ray CT, a high energy X-ray CT system and a soft X-ray phase contrast system are being developed respectively for high resolution reconstruction of internal structures of metal parts and polymer parts. The high energy X-ray CT uses dual X-ray sources (450KV & 225KV) to achieve big penetration depth with better imaging contrast and CT artifacts removal. The soft X-ray phase contrast imaging system uses a 60KV source and diffractive X-ray optics to encode and extract internal structure by phase information. Both systems adopt an open platform design which can be easily tailored for various applications and further research. 

3D image processing capabilities are being built up for the volumetric image registration and segmentation, 3D feature recognition and extraction, 3D calibration and measurements, and 3D visualization. Intelligent model based 3D image processing algorithms are being developed to achieve sub-voxel resolution for precision measurements. 

High speed CT reconstruction and 3D image processing is approached both at algorithm and hardware implementation levels. New sampling theory such as compressive sensing and parallel computation are being explored in development of CT algorithms, meanwhile with their hardware implementation on GPUs and FPGA is addressed. 

To manage the uncertainties in X-ray CT for measurements, modelling of interaction of X-ray with matters is also being investigated by using Monte-Carlo approach.


  • CT system instrumentation

  • CT algorithm development

  • 3D image processing (calibration, segmentation and registration), 3D visualization, 3D defect inspection and measurement,

  • High speed image processing,

  • Line scan large area image processing

  • Vision inspection systems for various applications lens inspection, wafer inspection, wire bond inspection, 2D X-ray to CT conversion, and BGA and wafer bump inspection.


Research Showcases