JP4079840B2 - Bar code reader and POS system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a barcode reader and a method for diffusing a projection light source used therein, and more particularly to a method for diffusing a projection LED used in a fixed CCD barcode reader.
[0002]
[Prior art]
Bar code readers are standardized such as JAN (Japanese Article Number) and UPC (Universal Product Code) printed on merchandise etc., which are installed in, for example, POS (Point Of Sales) systems placed at store cash registers. From the bar code, bar code information such as a country code, a manufacturing code, and a product type code is read according to the thickness and interval of the bar.
[0003]
In this barcode reader, a laser is used as a light source, the laser beam is scanned in a predetermined scanning pattern from one end of the barcode to the other end, the reflected light is received by a photodetector, and the barcode is based on the received light signal. Using a laser scanning bar code reader that reads information or an LED (Light Emitted Diode) as a light projection system to the light source, the light is irradiated onto the bar code and the reflected light is imaged on a CCD (Charge Coupled Device) In addition, a fixed CCD barcode reader that reads barcode information based on the CCD output is known.
[0004]
In addition, there are the following as prior art documents related to the present invention.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 61-054570 [Patent Document 2]
JP-A-2002-111970 [0006]
[Problems to be solved by the invention]
The above-described fixed CCD barcode reader is required to be installed in a small mounting volume, and downsizing is strongly desired. For this reason, particularly, the mounting volume of the light projecting system is reduced, and the barcode symbol irradiation is performed. There is a demand for uniform light distribution.
[0007]
The present invention has been made in consideration of such a conventional situation, and an object thereof is to reduce the mounting volume of the light projecting system and to make the distribution of the irradiation light to the barcode symbol uniform.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention includes a light projecting light source that emits irradiation light on a bar code symbol, and a light receiving unit that receives reflected light from the bar code symbol, and a light reception signal of the light receiving unit. In the barcode reader for reading the barcode symbol based on, the diffusion light is diffused so that the illumination light from the light source forms a uniform illumination distribution surface on the barcode symbol, and the diffusion The means is provided in the irradiating section of the projection light source , the diffusing means has a diffusing cap that covers the irradiating section of the projecting light source, and the diffusing cap receives the irradiation light from the projecting light source. It has a diffusion characteristic of diffusing so as to have a single mountain-shaped light amount distribution on the irradiation surface, and the light projecting light source has a plurality of LEDs, and the diffusing cap covers the irradiation portions of the plurality of LEDs. And The plurality of LEDs are arranged at positions facing each other on the barcode symbol, and the diffusion cap is arranged such that the LED arranged at a position facing the center side on the barcode symbol among the plurality of LEDs is characterized Rukoto which having a different spreading characteristics depending on the arrangement positions of the plurality of LED as the spread angle of the irradiation light than LED widens disposed on opposite positions on the end side on the bar code symbol And
[0011]
The diffusion means may comprise a diffusion uneven portion formed on the portion irradiated with the projection light source.
[0012]
The light receiving unit may include a solid-state imaging device. The solid-state imaging device can be exemplified by a CCD, for example, but may be other types.
[0014]
A POS system according to the present invention is characterized in that any one of the bar code readers described above is mounted.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a barcode reader according to the present invention and a method of diffusing a projection light source used therewith will be described below with reference to FIGS. The present embodiment is applied to a fixed CCD barcode reader mounted on a POS system or the like.
[0016]
FIG. 1 shows the overall configuration of a barcode reader 10 of the present embodiment. A bar code reader 10 shown in FIG. 1 has a plurality of projection light sources (in FIG. 1) that emit irradiation light toward a bar code symbol 20 from which bar code information is to be read. In the example, four LEDs 11a... 11d, a light receiving lens 12 that receives reflected light from the barcode symbol 20, and an electrical signal that forms the reflected light through the light receiving lens 12 and carries the barcode symbol image. And a CCD 13 that converts the light into a light and outputs it to the irradiating part of each LED 11a... 11d optically diffusing (diffuse transmission or diffuse reflection) so as to change the traveling direction of the irradiation light into many spatial directions. As a diffusion means having diffusion characteristics, a plurality of LED caps 14a to 14d for diffusion made of a predetermined optical material are individually covered.
[0017]
Here, the principle of the method of diffusing the projection LED used in the barcode reader of this embodiment will be described with reference to FIGS.
[0018]
FIG. 2 illustrates the light amount distribution of the irradiation light when the LED caps 14a... 14d are not attached to the irradiation portions of the LEDs 11a. In general, in the case of a barcode reader 10 having a CCD 13 in a light receiving portion, LEDs 11a. The LEDs 11a to 11d usually have variations in the angle of irradiation light, the amount of light, and the distribution of the amount of light. Therefore, in the optical configuration of the barcode reader 10 shown in FIG. 2C, when the LEDs 11a... 11d are used in combination, the waveform 1 in FIG. 2A and the waveform 2 in FIG. As described above, the light amount distribution unevenness generally occurs from the central portion C2 on the CCD 13 to both end portions E3 and E4. This is because there is variation in the light quantity distribution of the individual LEDs 11a.
[0019]
As a countermeasure, FIG. 3 illustrates the light quantity distribution of each LED 11a... 11d alone when the LED caps 14a. Fig.3 (a) shows the case where LED cap 14a ... 14d is not attached to the irradiation part of each LED11a ... 11d. In this case, the light quantity distribution of the irradiation light of each of the LEDs 11a to 11d has a plurality of peaks indicating the peak points of the light quantity distribution from the central part on the irradiation surface (barcode symbol surface) to both ends thereof (in the figure). In the example, there are three), and thus an unevenly distributed irradiation surface is formed.
[0020]
On the other hand, FIG.3 (b) shows the case where LED cap 14a ... 14d is attached to the irradiation part of each LED11a ... 11d. In this case, the light quantity distribution of the irradiation light of each LED 11a... 11d alone has its light quantity distribution peak from the center portion on the irradiation surface (barcode symbol surface) to both ends thereof due to the diffusion characteristics of each LED cap 14a. A single peak indicating a point has a gentle mountain-shaped distribution, thus forming a uniform distribution irradiation surface. In other words, each LED cap 14a... 14d used in the barcode reader 10 of the present embodiment is configured so as to have a diffusion characteristic capable of forming such a uniform distributed irradiation surface.
[0021]
When a plurality of (four in the example in the figure) LED caps 14a... 14d having diffusion characteristics capable of forming a uniform distribution irradiation surface are used in combination, the light quantity distribution formed on the irradiation surface is 4 The light quantity distributions of the individual LEDs 14a... 14d are synthesized.
[0022]
For this reason, in this embodiment, as shown in FIG. 4, the diffusion characteristics of the LED caps 14a... 14d to be put on each of the four LEDs 11a. That is, among the four LEDs 11a... 11d, the diffusion characteristics of the LED caps 14a and 14d attached to the outer two LEDs 11a and 11d are the same as each other as shown in FIG. It is configured so that the width (range) from the center to the end of the light quantity distributions a and d on the irradiation surface (barcode symbol surface) is narrow. On the other hand, the diffusion characteristics of the LED caps 14b and 14c attached to the two inner LEDs 11b and 11c are the same as each other as shown in FIG. 4B, and the spread angle α2 of the irradiated light is wide. The light quantity distributions b and c are configured to have a wide width from the center to the end.
[0023]
FIG. 5 illustrates the light quantity distribution characteristics of the barcode reader 20 of this embodiment in which the LED caps 14a... 14d having the diffusion characteristics as described above are provided in the irradiation portions of the LEDs 14a. In the optical arrangement of the barcode reader 10 shown in FIG. 5C, the LED caps 14a... 14d each covered with the LED caps 14a. As shown in FIG. 5C, the light amount distribution a... D of the irradiation light from the LED caps 14a... 14d is formed so that adjacent portions overlap each other on the irradiation surface (barcode symbol surface). The
[0024]
As a result, as shown in FIG. 5B, as a whole, a combined light amount distribution (A = a + b + c + d) is obtained by combining the light amount distributions a to d. As shown in FIG. 5B, the combined light amount distribution (A) is a pattern in which one gentle mountain is formed at the center, and a uniform distribution irradiation surface is formed as a whole. On the other hand, the light receiving distribution characteristic (B) of the light receiving lens 12 is a pattern in which one gentle valley is formed at the center as shown in FIG.
[0025]
Therefore, the distribution characteristics on the CCD 13 after passing through the light receiving lens 12 are, as shown in FIG. 5A, the combined light quantity distribution (A) of the LEDs 11a. The light distribution characteristic (B) of the light receiving lens 12 in which a gentle valley is formed in the central part is a distribution characteristic (A + B) synthesized with each other. A flat distribution characteristic is obtained.
[0026]
As described above, the LED caps 14a... 14d make the light distribution unevenness of the LEDs 11a... 11d alone, so that the effect of making the light distribution constant can be obtained even when a plurality of LEDs 11a. As a result, the light emitted from each LED 11a... 11d is diffused by each LED cap 14a... 14d to create a uniform irradiation distribution plane, and the barcode symbol 20 is irradiated with light without unevenness in light quantity, and the distribution is made uniform. The reflected light can be imaged on the CCD 13 via the light receiving lens 12.
[0027]
Therefore, according to the present embodiment, by providing an LED cap on the irradiating portion of each light emitting LED, the distribution of the amount of light irradiated on the barcode symbol becomes uniform, thereby eliminating the unevenness of the amount of light to the CCD and reading accuracy. Will be greatly improved. Further, since it is only necessary to cover the LED irradiation portion with the LED cap, for example, a space for attaching a diffusion plate to the peripheral portion of the LED is not required, which is particularly advantageous when realizing high-density mounting.
[0028]
In the above embodiment, the case where the LED cap having the above diffusion characteristics is provided as a diffusion method (diffusion means) for making the light quantity distribution of the LED uniform is described, but the present invention is not necessarily limited thereto.
[0029]
For example, the appearance of the irradiated part of an LED is usually a glossy surface, but the glossy part is scratched with a file or the like to form an uneven surface, and the irradiation direction of the irradiated light is spatially changed using the irradiated part appearance. It may be configured to diffuse in many directions. Further, a textured surface (predetermined uneven surface) is provided in advance on the mold for the irradiated portion used when processing the irradiated portion of the LED, and an uneven surface is formed on the irradiated surface of the LED according to the textured surface. You may comprise so that the advancing direction of irradiation light may be spatially changed in many directions and diffused using the irradiation surface appearance. In this case, it is preferable that the diffusion characteristic of each LED is configured such that the spread angle of the irradiation light and the light amount distribution width are different depending on the arrangement location as in the case where the LED cap is provided.
[0030]
【The invention's effect】
As described above, according to the present invention, it is possible to reduce the mounting volume of the light projecting system and make the distribution of the irradiation light to the barcode symbol uniform.
[Brief description of the drawings]
FIG. 1 is a diagram showing an overall configuration of a barcode reader according to an embodiment of the present invention.
FIGS. 2A to 2C are diagrams illustrating the light amount distribution of irradiation light on a barcode symbol surface when an LED cap is not attached.
FIGS. 3A and 3B are diagrams illustrating a light amount distribution of a single LED, in which FIG. 3A illustrates a light amount distribution when an LED cap is not attached, and FIG. 3B illustrates a light amount distribution when an LED cap is not attached; It is.
FIG. 4A is a diagram for explaining the spread angle and distribution of the two outer LEDs, and FIG. 4B is a diagram for explaining the spread angle and distribution of the two inner LEDs.
5A is a diagram showing a distribution characteristic after passing through a light receiving lens, FIG. 5B is a diagram showing a combined light quantity distribution of four LEDs and a light reception distribution characteristic of the light receiving lens, and FIG. It is a figure which shows each light quantity distribution of one LED.
[Explanation of symbols]
10 Bar code reader 11a ... 11d LED
12 Light receiving lens 13 CCD
14a ... 14d LED cap 20 Barcode symbol

Claims (4)

A barcode reader comprising: a light projecting light source that emits irradiation light on a barcode symbol; and a light receiving unit that receives reflected light from the barcode symbol, and reads the barcode symbol based on a light reception signal of the light receiving unit In
Diffusing means for diffusing the irradiation light so that the irradiation light from the light source forms a uniform irradiation distribution surface on the barcode symbol;
It said diffusing means is provided at the irradiation portion of the light projecting light source,
The diffusing means has a diffusing cap that covers the irradiating part of the light projecting light source, and the diffusing cap has a light distribution of one mountain shape on the irradiation surface of the light emitted from the light projecting light source. Has diffusion characteristics to diffuse
The light projecting light source includes a plurality of LEDs, and the diffusion cap is put on the irradiation portion of the plurality of LEDs.
The plurality of LEDs are arranged at opposite positions on the barcode symbol;
The diffusion cap is more than the LED in which the LED arranged at the position facing the center side on the barcode symbol among the plurality of LEDs is arranged at the position facing the end side on the barcode symbol. bar code reader, characterized in Rukoto which having a different spreading characteristics depending on the arrangement positions of the plurality of LED as the spread angle of the irradiation light becomes wider. The diffusion means, the bar code reader according to claim 1, wherein a diffusion uneven portion formed on the portion irradiated with the projection light source. The light receiving unit, the bar code reader according to claim 1 or 2, characterized in that it has a solid-state imaging device. A POS system comprising the barcode reader according to any one of claims 1 to 3 .

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