Jiang Lipei

Detecting linear features in weld seam images based on beamlet transform

Weld seam images are replete with noise and ordinary line detection algorithms such as Hough transform is not an ideal approach to extract significant linear features from it. We present a novel line detection algorithm based on beamlet analysis. The algorithm is described in detail after introducing the beamlet dictionary and beamlet transform. Taking into account of some special characteristics of welding image processing, we add an orientation-thresholding step to the standard beamlet-based line detection algorithm. Experiments show that our line detection algorithm is powerful in anti-noising and is especially suitable to detect linear features in heavily noisy weld seam images. We directly extracted one significant linear feature of the weld seam from both the original experimental image and the extra-noised images (SNR ges6 db) exactly and efficiently at scale 0 with the help of orientation threshold. Neither pre-processing nor post-processing of the image was performed. This implies that our algorithm can dramatically improve the efficiency of weld seam image processing.

3-D calibration method for freehand ultrasound image with high precision based on string-beads phantom

As extremely important techniques of MRCAS, Z-string-beads phantom and optimization algorithm for manual imaging coordinates are investigated to improve the precisions of 3-D ultrasound (US) calibration which defines the spatial relationship between the US image plane and an external tracking device attached to the US probe. The phantom consists of accurate position beads and two layers of Z-string planar arrays. The beads can rapidly guide the user to align the probe accurately for imaging, so their coordinates are directly used in the algorithm for homologous points matching without any transformations; the optimized algorithm incorporates the imaging points coordinates (mass centre coordinates of each point) in multiple US images that corrects the manual marking coordinates of the imaging points. The calibration parameters are calculated by matching of homologous points in the image and the tracking device and the 2-D US image can be converted into 3-D US coordinates. The results show that this method can simplify the calibration algorithm, reduce the influences of the US beam thickness on the precision and improve the calibration precision and reconstruction accuracy of the 3-D US system. The calibration experiments are demonstrated with a magnetic locator, but the method could be suitable for other tracking devices.

Research on 3-D Real-Time Measurement System of Seam with Laser

3-D Real-time Measurement System of seam outline based on Moiré Projection is proposed and designed. The system is composed of LD, grating, CCD, video A/D, FPGA, DSP and an output interface. The principle and hardware makeup of high-speed and real-time image processing circuit based on a Digital Signal Processor (DSP) and a Field Programmable Gate Array(FPGA) are introduced. Noise generation mechanism in poor welding field conditions is analyzed when Moiré stripes are projected on a welding work piece surface. Median filter is adopted to smooth the acquired original laser image of seam, and then measurement results of a 3-D outline image of weld groove are provided.

3-D calibration of ultrasound image for rural MRCAS

To reduce the cost of Medical Robotics and Computer Assisted Surgery (MRCAS) in rural medical of china, the researchers have focused on MRCAS investigation. They are inclined to select ultrasonography as medical image guidance because of its low cost, noninvasiveness and accuracy. 3-D calibration of ultrasound image is a very important technique of MRCAS. To improve the calibration precision, a method based on grid-string phantom and rapid algorithm for coordinate transformation is investigated. It accurately defines the spatial relationship between the US image plane and an external tracking device attached to the US probe. The phantom consists of two layers of grid-string planar arrays. The cross of the strings can rapidly guide the user to align the probe accurately for imaging; the cross coordinates are directly used in the algorithm for homologous points matching without any transformations. The calibration parameters are calculated by matching of homologous points in the image and the tracking device, then, the 2-D US image can be converted into 3-D US coordinates. The results show that this method can accelerate the speed of the calibration, simplify the calibration algorithm, reduce the influences of the US beam thickness on the precision and obtain the normal calibration precision and reconstruction accuracy of the 3-D US system.

Initial experiments of a needle-holding robot for microwave ablation therapy

A needle-holding robot for microwave ablation therapy is developed to free two hands of the surgeon, so that more effort can be concentrated on monitoring the ablation procedure, which in turn guarantees good tumor ablation effect. The overall architecture of the robot is introduced first with the explanation of the mechanism of 3D motion tracking and how to minimize damping force for the robotic hand. Two experiments were conducted, one to quantify the force required for motion tracking, the other to assess the performance of motion tracking. The results of force-measuring experiment show that the force required for rotation and radial translation motion tracking are less than 15 grams, which indicates the high sensitivity of the holding robot. The results of in-vivo animal test performed on a swine show that the holding robot is accurate enough in tracking the 3D motion of the ablation needle, which allows for stable and precise holding of the needle compared to that of freehand holding.

The study on 3D image laser sensing technology of welding seam

Using Moire Pattern technology, a 3D image laser sensing system of weld seam was introduced. The realization method of the system and its image processing were explained. 3D weld seam images were obtained with experiments.