Radiant energy – Photocells; circuits and apparatus – Photocell controlled circuit
Reexamination Certificate
1999-01-15
2001-04-24
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Photocell controlled circuit
C250S559100, C250S566000
Reexamination Certificate
active
06222178
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a bar code reading apparatus for detecting variations in intensity of reflected light from a bar code which is irradiated with laser beams scanned by a scanning optical system. The present invention relates more particularly to a bar code reading apparatus which can automatically decrease intensity of the laser beams and stop the scanning by the scanning optical system when unused.
2. Description of the Prior Art
A practice of managing merchandise and inventory by using bar codes has been popularized in recent years as represented, for example by a POS (point of sale) system in a distribution business. For example, in a POS system of a retail store, items of data such as kinds, sales prices, of the goods, etc. are encoded in a bar code format, and the encoded bar code is printed on the goods or printed on a label affixed to the goods. Then, the bar code is read at a cash register or postern, and the payment of the goods is made based on the read data. Subsequently, the numbers of sales of the goods are determined in real time, which can be useful for stocking, inventory, and purchasing management.
By the way, the above bar code reading apparatus for reading the bar code can be classified into a fixed type used when the goods are relatively small and a hand-held type used when the goods are relatively large. The fixed type involves the use of a mechanism for scanning the bar code with irradiated light beams in multi-directions so that the bar code can be read even when the goods are set over the bar code reader without an operator being aware of a direction of the bar code. More specifically, the fixed type uses a polygon mirror and fixed reflecting mirrors in combination. Laser beams acting as reading irradiated light beams are reflected by a single reflection surface of the polygon mirror, during which these reflected light beams are sequentially incident upon a plurality of fixed reflecting mirrors in order and deflected in a variety of directions for scanning. The bar code reading apparatus receives the reflected light beams from the surface of the goods during such scanning, and decodes the data encoded in the bar code on the basis of variations in intensity of the received light beams.
In this fixed type bar code reader, a laser diode used as a laser light source naturally has a finite usable life. Accordingly, if an emission of the laser beams continues even in a standby status where the reading of the bar code is not carried out although a power is supplied to the laser reading apparatus, the laser diode might require frequent replacement. Similarly, if the optical scanning system is constantly driven, a fault is more likely to occur, and a large quantity of electric power is unnecessarily dissipated.
Conventional bar code reading devices have attempted to solve these problems by utilizing a trigger switch or an item sensor in the vicinity of a bar code reading position (which may be an external surface of a glass plate inset in an outer wall of the bar code reading apparatus so that the laser beams penetrate it toward the outside). In the conventional bar code reading apparatus, an optical scanning system is driven and the laser beams are emitted only when the goods is detected by the trigger switch or the item sensor.
However, in cases where the goods are mechanically detected by the trigger switch or the item sensor, the operator must take steps to make the goods contact with the trigger switch or the item sensor. Hence, the operator has to perform the reading operation while being aware of the trigger switch or the item sensor.
SUMMARY OF THE INVENTION
It is a first object of the present invention, which was contrived in view of the above problems inherent in the prior art, to provide a bar code reading apparatus capable of efficiently starting an emission of laser beams and starting the drive of a scan optical system without making a user aware of an existence of a sensor. The invention has a construction which can optically detect an object marked with a bar code.
If a detecting apparatus for detecting an existence of an object in the vicinity of the bar code reading position based on from variations in a received light quantity is used, the apparatus can be offered at a low price. However, in this case, the object which detected is not always necessarily a commercial goods or an item which is intended to be scanned. By the way, if a time period since the goods has been once detected is short, there is a high possibility that the goods may be re-detected. Further, even if the irradiation of the laser beams and the drive of the scan optical system are restarted due to a misdetection, and if the goods is exposed to the laser beam in the bar code reading position during the restarted irradiation of the laser beams, this resumption of the irradiation of the laser beam is not useless.
It is a second object of the present invention to provide a bar code reading apparatus that decreases a sensitivity when detecting an object in accordance with a length of a time period for which the reading of the bar code is interrupted after once reading the bar code to reduce troubles or errors caused by the misdetection.
To accomplish the first and second objects of the invention, a bar code reading apparatus according to the present invention adopts the following constructions.
In a first aspect of a bar code reading apparatus of the present invention, a bar code reading apparatus comprises a laser light source for emitting laser beam. A scan optical system is provided for deflecting the laser beams toward a read position, and a demodulating element is provided for demodulating data encoded in a bar code marked on an object disposed in the read position on the basis of a reflected beam of the laser beam reflecting on the bar code. The bar code reading apparatus also comprises a power changing element for changing power of the laser beam from a normal level after a predetermined time has elapsed since the demodulating element performed the demodulation last time, and an optical sensor optically detecting an object disposed in the read position. The bar code reading apparatus further comprises a restoring element for restoring the power of the laser beams to the normal level when the optical sensor detects an object, and a sensitivity decreasing element for decreasing a sensitivity of the optical sensor in accordance with the elapsed time since the demodulating element performed the demodulation last time.
According to the first aspect of the bar code reading apparatus of the present invention, the laser light source emits the laser beam. The scan optical system rotates and deflect the laser beams toward the read position. The demodulating element detects the reflected beam of the laser beam reflected on the bar code marked on the object disposed in the read position, and demodulates the data encoded in the bar code. The power changing element changes power of the laser beam emitted from the laser light source from the normal level after the predetermined time has elapsed since the demodulating element performed the demodulation last time. The optical sensor optically detects an object disposed in the read position. When the optical sensor detects an object, the restoring element restores the power of the laser beams emitted from the laser light source to the normal level. The sensitivity decreasing element decreases the sensitivity of the optical sensor in accordance with the elapsed time since the demodulating element performed the previous demodulation. Accordingly, when the elapsed time since the demodulation has been previously performed is not so long, there must be a relatively small possibility of misdetecting an object other than the object marked with the bar code even if the detection sensitivity is increased because of such a high possibility that the bar code can be read. Further, it is possible to prevent a failure of detecting the object marked with the bar code by increasi
Itoh Motohiko
Iwaguchi Isao
Kawai Hiroaki
Satoh Shin-ichi
Shinoda Ichiro
Arent Fox Kintner & Plotkin & Kahn, PLLC
Fujitsu Limited
Le Que T.
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