Optical reader for bar coded labels.

摘要

A circular scan reader utilizes oscillating mirrors (34, 36) and associated optics (22, 24) to generate a circular scan pattern of laser light focused to a small spot. The angle of the scan emanating from a point just inside the reader through a window (21) forms a conical shape which permits scanning inside a yarn tube (10) without inserting any portion of the reader into the tube. When the scan passes over a bar coded label (12), the changes in reflection of light between the bars (12a) and spaces (12b) are detected by a photodetector (38) mounted on the face of the window (21). These fluctuations in light which correspond in width to the bar and space width are converted to an electrical signal that is amplified, and decoded. A driver circuit (50, 52, 53, 54, 55, 34, 35) for the oscillating mirrors controls the scan rate and scan pattern. The scan rate is modulated to cause a variation in the sweep depth in the tube thus providing an area scan. The area scan reduces the need for accurate label placement in the tube core.