A System Deployment Model of Multi-CCD Automatic Optical Inspection for Economical Operations

Abstract

Overkill and leakage are common problems in automated optical inspection (AOI) systems that have harmed firms to devote in intensive manual reinspection and seek the best CCD setting, resulting in more costly and less effective AOI operations. This study proposed a two-stage AOI based inspection system deployment model of multi-charge coupled device (CCD) for cost reduction; that is, the strictness decision model of a single CCD in the operational stage and switch on/off decision model of a set of CCDs in the strategic stage. The strictness decision model identifies the best strictness level of individual CCD by analyzing a confusion matrix according to the true defect rate of products. The multi-CCD switch decision model suggests the best switch on/off decision of multiple CCDs. Experiments in an electrical connector manufacturing plant revealed that the total inspection cost was the lowest when the strictness level was set close to the true defect rate. The best multi-CCD on/off strategy was more cost-effective than was the all CCDs-on mode under various strictness settings, by cost reduction up to 23.49%. In general, the proposed two-stage model achieves flexible multi-CCD settings of AOI systems and operations at a low cost. The proposed model can be extended to different applications of overkill and leakage problems. In this study, the proposed VGG-like convent five-layer convolution model learns from the experience of quality re-inspection personnel, which can be applied to the re-inspection line to identify AOI as defective images for re-inspection. The best accuracy reaches 99.21%.

Keywords

• Automated optical inspection
• charge coupled device
• confusion matrix
• cost-effective analysis
• inspection system deployment
• Type I & II errors