Resolution Metric
Performance characteristic measures the ability of an imaging system to transfer contrast from the object to the image at various levels of detail. In board inspection, the spatial frequency response quantifies the sharpness of the camera and lens combination when looking at fine features like solder bridges or micro vias. This value is expressed as a function of the number of line pairs per millimeter that the system can resolve.
System Evaluation
Analysis of the contrast loss at higher frequencies reveals the limit of the system’s ability to detect small defects. As the features on a PCB get smaller and closer together, the camera must be able to maintain enough contrast to distinguish them as separate entities. If the response drops too low, the edges of tiny components become blurry and the inspection algorithms cannot determine their precise location.
Factors like lens quality and sensor noise contribute to the final curve. Engineers use this metric to compare different inspection machines and ensure they are capable of handling the latest high density interconnect designs.
Data Quality
Sharpness at the pixel level ensures that the mathematical filters used for edge detection operate on reliable data. Poor response leads to high uncertainty in the automated measurement of trace widths and gaps.
