Two-dimensional bar-code detection system using a complementary laser light emission method

The use of two-dimensional bar codes in practical applications, such as product management for electronic parts and motor vehicle parts, has been studied recently. A new two-dimensional bar-code detection system using two visible-light laser diodes driven by complementary light emission and pulse modulation with a bias current near the threshold has been developed for applications such as goods management in production lines requiring high-speed detection. The pulse modulation drive with a bias current near the threshold achieves a light output rise time of 300 ns, which is much shorter than the 1.3 mu s it achieves without a bias current. The effective scanning speed of 950 scan/s is twice that of the conventional two-dimensional raster scanners. It has been clarified experimentally that this scanning speed is limited by the bandwidth of the photodetection amplifier.