1. Technical Field of the Invention
The present invention relates generally to a bar code reader designed to read a bar code using a laser beam, and more particularly to an improved bar code reading apparatus capable of reading a bar code with decreased power consumption.
2. Background of Related Art
FIG. 3 shows a conventional bar code reader which includes a laser-emitting device consisting of a trigger switch 1, a laser controller 2, a laser source 3, a mirror driver 4, and a mirror 5. The trigger switch 1 is responsive to depression of a switch (not shown) to provide operation start signals to the laser controller 2 and the mirror driver 4 and activates them. The laser controller 2 outputs an excitation signal to the laser source 3. The laser source 3 emits a laser beam to the mirror 5. The mirror 5 includes, for example, a polygon reflector which is rotated by the mirror driver 4 to reflect the input laser beam for scanning a bar code printed on a bar code label 6 attached to an article.
The bar code reader also includes a laser-receiving device consisting of an optical sensor 7, a binary-coding circuit 8, a counter 9, a sampling clock generator 10, and a CPU 11. The optical sensor 7 consists of a photoelectric converter that converts an input laser beam reflected from the bar code label 6 into an electric analog signal according to the intensity of the laser beam. The binary-coding circuit 8 converts the analog signal outputted from the optical sensor 7 into a digital signal and outputs it to the counter 9. The counter 9 counts clock signals supplied from the sampling clock generator 10 according to the input digital signal to provide a numerical code signal indicative of the width of one of bars or spaces between the bars of the bar code and outputs it to the CPU 11. The CPU 11 decodes the numerical code signal to provide bar code information.
The above conventional bar code reader, however, has the drawback in that the laser source 3 continues to output a laser beam once turned on regardless of whether or not the bar code reader is at a location where it is possible to read the bar code correctly, and the CPU 11 decodes the numerical code signal each time it is outputted from the counter 9 regardless of whether the bar code has been picked up correctly or not. This wastes the power of the bar code reader.