TITLE:
A High-Density Ternary Barcode Detection System with a Dual-Bias Differential Method
AUTHORS:
Hiroo Wakaumi
KEYWORDS:
Optical Detection System; Laser Diode; Barcode; Ternary; Signal Processing; Simulation
JOURNAL NAME:
Journal of Sensor Technology,
Vol.3 No.1,
March
27,
2013
ABSTRACT: A dual-bias differential
method is presented for increasing the detection range of a ternary barcode detection
system. The system is provided with a second differential delay circuit with
bias control to process optimally gray signals by lowering their averaged level
using a clamping circuit. This is added to the primary conventional
differential delay circuit without bias control and a comparator to process
optimally black signals based on the envelope-differential fixed-period delay
(EDFPD) detection technique. This method enables the system to detect over a
longer range at high speeds while being capable of handling a large amount of
information. The estimate results of gray and white code widths against the
clamp bias made through the dynamic operation simulation of a differential
circuit using SPICE were nearly consistent with the experimental results.
Thereby we can conclude that the dynamic simulation is effective for estimation of an optimum clamp bias
voltage. It was confirmed that the detection range of the system with a clamp
bias voltage of ?0.4
V for a minimum bar width W = 0.25 mm was 1.4 times that of the conventional
EDFPD detection technique. In addition, the system operated at a maximum
scanning speed of 7.7 times that of conventional CCD cameras under the
practical detection range. The system with clamp bias control is expected to
enable the real-time identification of goods on production lines and in automated
warehouses.