This paper describes a 3 -D laser scanning imager for visual inspection of mounted devices on printed circuit boards (PCB). A 3 -D imager for this application must satisfy the following requirements: (1) It must be fast enough to sense a 250 by 330 mm area in 14 seconds; (2) It must have a measurement resolution of at least 125 Fun; (3) It must be capable of measuring height and light intensity simultaneously; and (4) It must have an optical dynamic range of at least 104.We developed a wide -area telecentric scanning optical system which meets these requirements. It uses retroreflective triangulation optics and digital signal processing hardware.Our system scans a laser beam over a 256 mm length with a resolution of 125 Fun, without scanning distortion. The retroreflection triangulation optics collect light reflected from objects on a printed circuit board and focus the image on a position-sensitive detector (PSD). This system measures the profile of objects with a vertical resolution of 30 im, within a range of 7.6 mm.The digital signal processing hardware has a dynamic range of 104 and obtains range data from the output signals of the PSD. Its processing speed is 1M pixels /s. This hardware enables profile measurement of objects having a wide range of light reflectance (about 3000 times), from black devices to glossy metal, with an accuracy of 0.1 mm.This 3 -D imager was used in an automated inspection system for PC board-mounted devices. This system detects missing, misplaced, and incorrectly installed devices with an inspection speed of 0.1 s/device.

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