Spatial Scanning
Optical inspection of populated circuit boards requires sequential imaging of localized surface regions to achieve the necessary resolution. The process of field of view stepping involves moving an image sensor or the circuit board in a series of discrete displacements to cover the entire assembly. This method ensures that high-magnification lenses can capture minute solder joints and component markings without loss of clarity.
Each step stops briefly to allow the camera to capture an image before advancing to the adjacent region.
Throughput Factor
Mechanical travel and stabilization times constitute a large portion of the total inspection cycle. In high-speed surface mount lines, the inspection system must coordinate the acceleration and deceleration of the optical head to prevent motion blur. Choosing larger sensor formats or increasing the pixel size can reduce the number of discrete steps required for a given board area, although this often reduces spatial resolution.
Advanced systems synchronize the strobe of the illumination source with the motion of the head to capture images without stopping the gantry, which minimizes the physical delay between steps.
Positioning Accuracy
Precision linear motors and glass-scale encoders control the positioning of the optical assembly during these movements. These components ensure that each individual image frame aligns perfectly with the board coordinate system. Accurate calibration of this motion prevents stitching errors at the boundaries of adjacent images.
