초록 ▼

A differentiation signal DF differentiated by a differentiation unit is inputted to a slice level generation unit and to comparators. A first peak-hold circuit and a voltage division circuit generate a slice level having a slice ratio SLR that is constant to a peak value VDF of the differentiation s

A differentiation signal DF differentiated by a differentiation unit is inputted to a slice level generation unit and to comparators. A first peak-hold circuit and a voltage division circuit generate a slice level having a slice ratio SLR that is constant to a peak value VDF of the differentiation signal DF. A second peak-hold circuit generates a slice level the slice ratio SLR of which changes in accordance with the peak value VDF. The slice level generation unit outputs their synthetic slice level SLL, which is compared by the comparators with the level of the differentiation signal DF, outputting thereby binarized signals W-GATE and B-GATE. When the level of the differentiation signal DF is high, the slice level SLL approaches the peak value VDF. Therefore, noise components contained in the differentiation signal DF cannot exceed the slice level SLL. When the level of the differentiation signal DF is low, the slice level SLL has a constant ratio to the peak value VDF. Consequently, the peak value of the amplitude of the differentiation signal DF can be detected reliably.

대표청구항 ▼

1. An optical code reader comprising:a scanning mechanism for radiating beams for scanning a code to be read; a beam receiving element for receiving reflected beams from a scanned object and outputting an electric signal; a differentiation unit for differentiating said electric signal and outputting

1. An optical code reader comprising:a scanning mechanism for radiating beams for scanning a code to be read; a beam receiving element for receiving reflected beams from a scanned object and outputting an electric signal; a differentiation unit for differentiating said electric signal and outputting a differentiation signal; a slice level generation unit for outputting a slice level which is made by synthesizing a first slice level and a second slice level, said first slice level having a first slice ratio which is constant with respect to a peak value of an amplitude of said differentiation signal and said second slice level having a second slice ratio, which varies according to said peak value, with respect to said peak value, where first and second slice ratios are ratios between a slice level and said differentiation signal; and a comparison unit for comparing the level of said differentiation signal with said synthetic slice level and outputting a binarized signal.