Visual inspection system to detect connector tilts in PCBAs
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Date
2005
Authors
Vithyacharan, Retnasamy
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Abstract
AVI’s are playing important roles in quality inspection in the
electronic industry. Most existing AVIs are single overhead camera and are
incapable detecting 3D defects. This thesis presents the development of a
single camera visual system to detect tilt of a Peripheral Component
Interconnect (PCI) connector on a Printed Circuit Board Assembly (PCBA). The
visual system developed consists of a personal computer, digital camera, slide
projector and a mirror. The problem in the current research and the objective is
to detect tilt in a PCI connector using a single overhead camera. The distortion
severity in the imaging system was initially studied to decide the need for
camera calibration. An equation was formulated experimentally to determine the
scaling factors at different height levels of object surface for converting image
pixel coordinates into physical dimension. The slide projector was used for
projecting sinusoidal fringes onto the surface under study. Phase-shifting was
achieved using a mirror mounted on rotary stage. Since the light source used is
non-collimated, i.e. the incident angle varies along x-, y- and z- directions, a
calibration exercise was carried out to obtain an equation for the incident angle
of the beam along the length of the object surface for different object height
levels. Solid glass blocks were initially used in place of actual PCI connectors to
test and verify the system. The phase-shifting technique was applied to
calculate the tilt angles on the glass blocks and later applied to the actual
connectors. This visual system developed using phase-shifting technique
demonstrates successful tilt detection and measurement in a PCBA. Compared to existing system the proposed system uses single overhead camera , noncollimated
light source and phase shifting technique to detect tilt on a connector
mounted to a PCBA.
Description
Master
Keywords
Mechanical Engineering , Printed Circuit Board Assembly