Research Projects

In-situ X-ray 3-D Inspection for Industry Applications

Inspection technology using 2-D X-rays and CT are now essential tools for detection and analysis of hidden defects in the automotive, advanced materials, semiconductor and electronics industries. This project is aimed to investigate and develop high-resolution, high-speed, in-situ 2-D and 3-D X-ray inspection technology systems. With the expertise and knowledge gained, we are able to provide services and technical support for a wide range of applications such as:

  • High-resolution 2-D/CT hidden defects inspection
  • Material characterisation using X-rays and gray-level based layer thickness measurement
  • Universal central ray determination technology for various scanning modes
  • Multi-layered planar object reconstruction and layer-separation with a preferred orientation
  • FPGA accelerated CT reconstruction
  • Carbon Nanotube X-ray source
Contact PersonLiu Tong()
Solution

Solution to problem 1: A universal centre-of-rotation determination method was developed. This method does not require any prior calibration or reference look-up table. It determines the centre-of-rotation directly using the scanning data of the object to be inspected and it has been proven to be very effective for various scanning modes, such as normal, high-magnification and offset-scans. This method works very well when large variation in X-ray intensity during the scanning is encountered or when poor image contrast is achieved during inspection of light materials.

 

Solution to problem 2: Two automated methods have been developed for this problem. One method is to automatically identify the exact scanning start orientation of the object from the sonogram of the projection data and do the reconstruction based on that identified angle. This method is simple in concept, easy to implement and add almost no extra computing time to the whole image processing process. The second method is to identify the orientation through applying Hough transform after reconstructing one slice. Once the orientation is calculated, reconstruction will be conducted based on that particular orientation.

 

Solution to problem 3: CNT has been proven capable of generating stable electron emission based on field-emission mechanism. SIMTech is currently testing their compact CNT X-ray source. If it is successful, it will become a potential replacement to the current bulky X-ray source, thus, making it possible to manufacture a portable, high-resolution X-ray inspection system.

Benefits
  1. T. Liu, A. A. Malcolm and J. Xu, "Universal method for centre-of-rotation determination in computed tomography technology" (ID-FY06-011, 2006)

    Description: Traditional CT scanning requires the prior calibration of the centre-of-rotation, usually by scanning a wire phantom. This invention provides a universal method for centre-of-rotation determination directly based on the projection data of the object. By measuring the mismatching level of two CT images of the same slice, respectively reconstructed by part of the total projections, the error to the true centre-of-rotation can be evaluated and minimised. This invention works well for almost all possible scanning modes, such as normal scanning, high-magnification scan and offset scan. It can also serve as a measurement tool for evaluating the reconstruction quality.

  2. T. Liu, A. A. Malcolm and J. Xu, "CT reconstruction method for planar objects with automatically determined orientation," (ID-FY06-008, 2006)

    Description: Multi-layered electronics are now increasingly popular in electronics design and advanced packaging industries. How to efficiently separate and visualise these layers are becoming necessary and important. This invention provides a method to reconstruct a planar object with a preferred orientation so that the layer separation and display become straightforward and simple, which can be achieved by just slicing the reconstructed object along one dimension of the coordinate system. Comparatively, traditional technology requires either to perform an image rotation to all reconstructed slices, or to manually measure the orientation angle with respect to a reference plane after reconstructing one slice, and then redoing the reconstruction, or to cut the object along a very carefully defined cutting plane.

  3. A .A. Malcolm and T. Liu, "Automated Determination of Object Orientation for CT Reconstruction", (ID-FY06-010, 2006)

    Description: Generally, CT systems perform reconstruction with the object orientated at some arbitrary angle. This invention provides a means to measure the orientation.

  4. T. Liu and A. A. Malcolm, "A method to improve the performance and efficiency of micro-CT systems for industrial applications", (ID-FY05-009, 2005)

    Description: Currently, CT developers and end-users are still looking for efficient and fast approach for field calibration of important system parameters. This invention provides a precise and economic method for simultaneous field determination or calibration of the source-to-object distance (SOD), the effective X-ray camera pixel size, the central-channel and the central rotation axis.

  5. T. Liu , "Computed tomography with central ray determined by projections of the part to be inspected", (ID-FY05-007, 2005);

    Description: All micro computed tomography reconstruction algorithms require the prior knowledge of central ray which is the projection of the centre-of-rotation. Traditionally, this is achieved by scanning a wire phantom and determining the centre of the projection sinogram. This is a manual process that not only requires more scanning and processing time, but also may generate errors because of mechanical movements involved, particularly with high-magnification CT scanning. This invention provides a method which allows us to directly determine the central ray with the projection data of the object to be inspected, thus greatly simplifying the CT scanning processing, saving time and effort and making automation of the whole CT process possible.

Patents / Awards / Achievements / Differentiation
  1. T. Liu, A. A. Malcolm and J. Xu, "Universal method for centre-of-rotation determination in computed tomography technology" (ID-FY06-011, 2006)

    Description: Traditional CT scanning requires the prior calibration of the centre-of-rotation, usually by scanning a wire phantom. This invention provides a universal method for centre-of-rotation determination directly based on the projection data of the object. By measuring the mismatching level of two CT images of the same slice, respectively reconstructed by part of the total projections, the error to the true centre-of-rotation can be evaluated and minimised. This invention works well for almost all possible scanning modes, such as normal scanning, high-magnification scan and offset scan. It can also serve as a measurement tool for evaluating the reconstruction quality.

  2. T. Liu, A. A. Malcolm and J. Xu, "CT reconstruction method for planar objects with automatically determined orientation," (ID-FY06-008, 2006)

    Description: Multi-layered electronics are now increasingly popular in electronics design and advanced packaging industries. How to efficiently separate and visualise these layers are becoming necessary and important. This invention provides a method to reconstruct a planar object with a preferred orientation so that the layer separation and display become straightforward and simple, which can be achieved by just slicing the reconstructed object along one dimension of the coordinate system. Comparatively, traditional technology requires either to perform an image rotation to all reconstructed slices, or to manually measure the orientation angle with respect to a reference plane after reconstructing one slice, and then redoing the reconstruction, or to cut the object along a very carefully defined cutting plane.

  3. A .A. Malcolm and T. Liu, "Automated Determination of Object Orientation for CT Reconstruction", (ID-FY06-010, 2006)

    Description: Generally, CT systems perform reconstruction with the object orientated at some arbitrary angle. This invention provides a means to measure the orientation.

  4. T. Liu and A. A. Malcolm, "A method to improve the performance and efficiency of micro-CT systems for industrial applications", (ID-FY05-009, 2005)

    Description: Currently, CT developers and end-users are still looking for efficient and fast approach for field calibration of important system parameters. This invention provides a precise and economic method for simultaneous field determination or calibration of the source-to-object distance (SOD), the effective X-ray camera pixel size, the central-channel and the central rotation axis.

  5. T. Liu , "Computed tomography with central ray determined by projections of the part to be inspected", (ID-FY05-007, 2005);

    Description: All micro computed tomography reconstruction algorithms require the prior knowledge of central ray which is the projection of the centre-of-rotation. Traditionally, this is achieved by scanning a wire phantom and determining the centre of the projection sinogram. This is a manual process that not only requires more scanning and processing time, but also may generate errors because of mechanical movements involved, particularly with high-magnification CT scanning. This invention provides a method which allows us to directly determine the central ray with the projection data of the object to be inspected, thus greatly simplifying the CT scanning processing, saving time and effort and making automation of the whole CT process possible.

Applications
  • Hidden defects inspection in semiconductor, electronics, automotives, advanced materials and aerospace industries
  • Layer separation and analysing in multi-layered structures
  • High-resolution 3-D inspection of small components
  • Fast thickness measurement of internal layers
  • Portable and in-situ X-ray inspection
Problems Addressed

Problem 1: Centre-of rotation is an essential parameter for all CT reconstruction algorithms. The precision of the final reconstruction depends on the accuracy of the rotation. Traditionally, this parameter is achieved either by calibration using a scanning calibration unit, which is time-consuming and tedious; or referring to a look-up table, which can provide errors and inaccuracy.

 

Problem 2: Multi-layered electronics are now increasingly popular in product design and advanced packaging. As a result, layer separation and visualisation is becoming very important method for localising and analysing any suspected defects. Traditionally, CT technology always reconstructs an object with a previously unknown orientation. This very often leads to a very complicated layer separation process. The current common practices are either to perform image rotation for all reconstructed slices, or to manually measure the tilted angle of the reconstructed slice and re-do the reconstruction, or after the reconstruction, to cut the 3-D reconstructed object by carefully defining a clipping plane.

 

Problem 3: Modern high-resolution X-ray system usually adopts a transmission mode and uses thermionically emitted electrons for X-ray generation. This kind of source is very bulky and heavy due to generally the cooling system and the complex mechanism for obtaining a small spot-size.