Infrared thermal imaging method was applied for the development of a non-destructive inspection technique to
determine the quality of resistance spot welds. The current work is an initial feasibility study based on post-mortem
inspection. First, resistance spot welds were fabricated on dual phase steel sheets (DP 590 steel) with carefullycontrolled
welding parameters. It created welds with desirable and undesirable qualities in terms of nugget size,
indentation depth, and voids and cracks. Second, five different heating and cooling methods were evaluated. The heating
or cooling source was applied on one side of the weld stack while the surface temperature change on the other side of the
weld was recorded using an infrared camera. Correlation between the weld quality and the "thermal signature" of each
weld was established. Finally, a simplified thermal finite element analysis was developed to simulate the heat flow
during inspection. The thermal model provided insight into the effect of the nugget size and indentation depth on the
peak temperature and heating rate. The results reported in this work indicate that the IR thermography technique is
feasible for weld quality inspection due to the distinguish temperature profiles for different welds and the repeatability
and consistency in measurement.
Today zoom optical system is more used in many fields. It can be satisfied with many special imaging instances with its
superiority on ability of supplying different visual field and resolution. But the conventional zoom system must have
more than two moving elements to realize focus turning and imaging shift compensation at the same time. This makes
the system have large volume and weight, and complicated structure. Liquid lens is a kind of novel optical device based
on biological vision system. By utilizing this device, zoom camera can be designed in a new simple way. In this paper, a
liquid lens operated by a stepper motor had been demonstrated. A new way of designing a micro zoom system without
any moving lens had also been introduced. And a kind of hybrid diffractive-refractive liquid lens had been presented to
improve the imaging quality. A micro bifocal zoom endoscope system including two pieces of liquid lens was contrived.
Finally, it is thought that although many technologies, especially the package method should be solved better, the liquid
lens micro zoom system has very wide potential application in the fields that the system's volume and weight are strictly
limited, such as endoscope, mobile, PDA and so on.