Visual inspection system using multidirectional 3-D imager

This paper describes a visual inspection system for factory automation. The system is based on a multi-directional 3-D imager. Three dimensional object recognition has become increasingly important in factory automation. For example, automatic assembly of printed circuit (PC) boards can use a 3-D visual inspection system to detect incorrectly assembled devices. To be effective, measurement should be done from more than one angle. A visual inspection system has been developed based on a multi-directional 3-D imager and laser cross scanning. It can obtain range and intensity information of objects simultaneously. Range measurement is based on laser triangulation using a position sensitive detector. The system features: (1) Multi-directional 3-D measurement. The quad 3-D imager and X-Y laser scanner enable multi-directional 3-D measuremenL (2) High-speed. Measurement speed is 1 million pixels per second. Each pixel contains data for 256-height-level range and 256-gray-level intensity. One quad flat package with 160 leads can be measured in 4 seconds. (3) High-resolution. The inspection resolution is 25 jim in the X and Y directions and 30 pm in the Z direction. The visual inspection system uses the 32-bit MC68030 and 12 megabytes of image memory. The system was capable of detecting missing, shifting, and floating leads, and solderjoint defects.