1. Field of the Invention
The present invention relates to an optical information reading method and device for optically scanning bar codes and like information via a laser beam emitted from a laser light source, and more specifically relates to an optical reading method and device suitable for scanning a bar code and like information via a downwardly directed laser beam.
2. Description of the Related Art
Conventional laser bar code readers of the installed type such as, for example, Spectra-Physics, Inc. (U.S.A.) model 750SL, and Nippondenso model BLS-1000, have a reader unit with a built in laser light source, a scanning unit and a reader unit arranged directly above the register counter of a supermarket or the like via a column support. A laser beam emitted from the laser light source of the scanning unit is emitted downwardly from a window on the bottom side of the unit and scans the bar code of the merchandise to accomplish a reading of the bar code information.
In laser bar code readers of the aforesaid construction, the laser beam for scanning the bar code of the merchandise is emitted downwardly from a window formed on the bottom side of the unit, as previously described, such that the bar code reading operation is readily accomplished on the register counter. Furthermore, such a bar code reader is safe because the laser beam is situated so as to not directly enter the eyes of an operator.
This advantage, however, also produces certain disadvantages because the laser beam is emitted downwardly, the disadvantages being described hereinafter. Normally, an operator removes the merchandise from the shopping basket disposed in proximity to the laser bar code reader on the register counter by a shopper, and after the bar code of said merchandise is read via scanning by the laser beam of the bar code reader, the merchandise is placed in another shopping basket on the register counter. It happens that sometimes the bar code of merchandise remaining in the shopping basket placed by a shopper and the bar code of merchandise already read and placed in the other shopping basket are scanned so as to be read together by the laser beam. Such a situation is disadvantageous inasmuch as the bar codes of the merchandise are duplicated, and the operator must perform an operation to correct the duplicated reading.
It has been considered that in order to prevent the aforesaid duplicate reading of the merchandise bar code, light having a wavelength near the wavelength of the laser beam should be directed toward the bar codes of the merchandise accommodated in the baskets. However, the aforesaid arrangement has certain disadvantages inasmuch as it requires an adequate light source to produce the aforesaid light having another wavelength, it requires more electrical power for said light source, and it is disadvantageous in terms of limitations to the location of installation.