Optical Response
Highly polished metallic and liquid surfaces reflect light directly back into camera lenses, causing bright spots and blind glares on digital images. Managing specular reflectance is critical during automated solder joint inspection, because lead-free alloys form curved, highly reflective surfaces when they solidify. This reflection pattern can hide cracks or insufficient fillet height from standard vision algorithms.
Sensor Saturation
High light levels from directly reflected illumination saturate the pixels on the camera sensor, leaving zero surface detail in the white regions of the image. When specular reflectance occurs on a solder fillet, the algorithm cannot determine the shape or volume of the joint. This problem is solved by using diffused dome lights and polarizing filters that soften the incoming light before it reaches the camera sensor.
These lighting setups ensure that the system gets clear pictures of curved solder connections.
Illumination Control
Controlling the angle and intensity of multiple light sources prevents the formation of bright glare spots on highly reflective board assemblies. By sequentially activating different LED rings, the system collects multiple views of the same joint to compile a complete profile. This technique ensures high defect coverage despite the challenging surface properties of lead-free joints.
