Electronics manufacturing throughout the world now uses an increasing percentage of Surface Mount Technology (SMT). The compact and light‐weight surface‐mounted components offer a number of advantages to manufacturers. Unfortunately, however, these same beneficial characteristics make the quality of the product difficult to guarantee. As miniaturisation continues, the inspection problem becomes worse, and so advanced methods of inspection are required. Automatic inspection systems already exist, although an effective, inexpensive and reliable system has yet to be found. Recent work carried out within the Coherent and Electro‐Optics Research Group at Liverpool Polytechnic has looked at the feasibility of applying some of its established inspection methods to the problem of solder joint inspection. Extensive development must still take place; however, the methods employed have shown promise. The system uses structured light techniques to add height information to an image of the solder joint under inspection. In this way a 3‐D image of the joint may be built up, digitised and processed in a computer at high speed in order to determine its quality.
Digital images contain a great many samples of light intensity distribution as recorded by a vision system. Processing times using software techniques can be relatively long due to the large number of samples, and real-time operation may be impossible. The paper considers the principles of edge detection and shows how they may be applied in a real-time system. It is shown that very large scale integrated circuits may be utilised to give efficient edge detection providing the camera system operates in a non-interlaced mode.
A technique is described for automatically determining the loss of material in an engineering component due for example to wear or corrosion. The system is based on the subtraction of two digital images of two contour maps of the surface of the object in its worn and unworn state. Calibration tests give an accuracy within 5%.
A novel measurement and inspection system for the detection and measurement of surface defects, such as chips and cracks, has been developed and applied to engineering components such as cylindrical rollers.
