Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-03-20
2002-10-22
Le, Que T. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S208100, C250S566000
Reexamination Certificate
active
06469294
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on, and claims priority to Japanese Patent Application 9-208137, filed Aug. 1, 1997 in Japan, and which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates in general to an optical scanner, and in particular, to a method of and device for reducing the beam diameter of separate light beam components emitted from a common light source for optical scanner.
BACKGROUND OF THE INVENTION
Point of Sale (POS) systems, such as optical scanners, capable of detecting and reading light reflected from a bar code attached to a commodity are widely used. For example, optical scanners, which are also referred to as bar code readers, are used at “check-out” counters in grocery stores to scan a bar code attached to a commodity such as a food product. By manipulating the commodity, these optical scanner systems provide an operator, such as a cashier, using the system to reduce the amount of time it takes to “scan” information about the commodity, reducing the burden on the operator and increasing the operator's efficiency.
In recent years, optical scanners with two reading windows have been developed. The two windows are provided, for example, in the bottom and front portions of the optical scanner, forming an “L” shape. The two windows enable the optical scanner to read and scan from multiple directions bar codes attached to commodities. Hence, a bar code attached to a commodity may be detected and read from light sources emitting from both windows, despite differing orientations of the bar code on the commodity. This feature further lightens the burden imposed on the operator. However, conventional optical scanners with multiple windows require separate optical scanners for each window. The result is a costly, complex optical scanner with numerous parts and which is large in size.
For example, optical scanners which have reading windows respectively provided in both the bottom and front portions thereof require optical scanning systems for each of the reading windows. Each of the optical scanning systems includes a light source, scanning means such as a polygon mirror, and other mirrors. Thus, the scanner is complex and requires a large number of components or parts, which increases the manufacturing costs. However, if a common light source is used for both of the optical scanning systems, the required number of parts and the costs associated therewith decrease.
The use of a common light source
1
in an optical scanner
100
is shown in FIG.
27
.
FIG. 27
is an exemplary prior art diagram illustrating a conventional optical scanner
100
with a common light source
1
and used, for example, to scan a bar code attached to an object. To use a common light source
1
in the optical scanner
100
shown in
FIG. 27
, a light splitting device
2
, such as a half mirror (semi-transparent mirror), is used to split a common light source
1
into a first light beam component X and a second light beam component Y. The first and second light beam components X and Y, respectively, are then directed to a common polygon mirror
3
, either directly or through another mirror. Light beam component X is then emitted through a group of mirrors M
1
from reading window
4
(provided in the bottom portion of the optical scanner
100
), and light beam component Y is emitted through a group of mirrors M
2
from reading window
5
(provided in the front portion of the optical scanner
100
). The emitted light beam components X and Y then impinge on, for example, a bar code attached to an object passing through the emitted light, which reflects back to the optical scanner
100
. The bar code is read by the optical scanner
100
by detecting the reflected light by detectors
6
and
7
.
In order to more accurately read a bar code, and in particular, a bar code having narrow spaces between adjacent bars, the beam width of the light beam scanning the bar code must be sufficiently reduced. To reduce the beam width of the light beam scanning the bar code, for example, light beam components X and Y (shown in FIG.
27
), a beam shaping device
8
is placed between the common light source
1
and the light splitting device
2
. Moreover, it is also necessary not only to reduce the diameter of the light beam components X and Y, but to reduce the diameter at a desired position. That is, the diameter of the beam size must be sufficiently reduced at the desired position, particularly the position where the object is being scanned.
As the width of the bars in the bar code narrows, it becomes increasingly difficult for an emitted light source to read the bar code. A desirable solution to reading bar codes having narrow spaces between bars would be to use a common light source
1
having a smaller diameter. As discussed above, it is desirable to “split” the common light source
1
(i.e., laser beam) into first and second laser beam components X and Y, such that the bar code may be read or scanned from multiple directions (from a bottom portion and a front portion of the optical scanning device). Using the first and second laser beam components X and Y, respectively, an “optimum reading zone” is established by defining first and second focal points of the first and second laser beam components X and Y, respectively. It is desirable that the focal point (a point at which the laser beam has the smallest diameter) of the laser beam is established near the reading center the optimum reading zone. In this regard, the common light source
1
is able to read and scan the bar code with increasing efficiency when the two focal points are directed towards the same location. To accomplish this, it is desirable that the distance from the light source from which the scanning light (light beam component X in
FIG. 27
) emitted from the bottom reading window
4
to the reading center is equal to the distance from the light source from which the scanning light (light beam component Y in
FIG. 27
) emitted from the side reading window
5
to the reading center.
However, due to the complexity of the optical components in the optical scanner for prior art, it is difficult to equalize these distances and may result in the focal point of the first light beam component X being set at the center of the optical reading zone, and the focal point of the second light beam component Y being set off-center of the optimal reading zone. In that case, the bar code cannot be read using the second scanning light. Hence, achieving optimal first and second focal points is hindered, resulting in the failure of one of the laser beam components from reading or scanning the bar code as it passes through the “optimum reading zone”.
Thus, there exits a need for a cost effective optical scanner having multiple windows which reduces the overall size of the scanner by reducing the number of components required therein. Additionally, there exists a need for an optical scanner having multiple windows capable of reading and scanning a bar code using a common light source.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an optical scanner which reduces the beam diameters of two light beam components into which a light beam emitted from a common light source is split by an optical beam splitter.
Another object of the present invention is to provide an optical scanner which is provided with a common light source and two reading windows, and which can read a bar code with good sensitivity by using light beams respectively emitted from the reading windows.
In accordance with one embodiment of the present invention, an optical scanner includes a body, at least one reading window provided in the body, a light source, light splitting means for splitting a light beam emitted from the light source into a first light beam component traveling along a first optical path, and a second light beam component traveling along a second optical path. Also provided in the optical scanner of the present invention are light scan means allowing the first light beam compo
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Le Que T.
Staas & Halsey , LLP
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