JP2001092920A - Bar code reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep a signal level higher than fixed output by always monitoring fluctuation or attenuation in the quantity (power) of laser light. SOLUTION: Concerning the bar code reader for reading the contents of a bar code 9 by irradiating the bar code 9 with output light from a light source 1 and receiving the reflected light with a light receiving element 11, light to irradiate the bar code 9 is received by a light receiving element 50. Corresponding to the quantity of light received by this light receiving element 50, a light source output control circuit 12 is controlled and the quantity of output light is changed. In this case, when the quantity of light received by the light receiving element 50 is reduced rather than a predetermined first level, the quantity of output light is controlled to be increased. Besides, when the quantity of received light is reduced rather than a second level lower than this first level, an alarm is outputted such as turning on an alarm lamp 13 so that the exchange of the light source 1 can be called.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bar code reader, and more particularly, to irradiating a bar code with output light from a light source.
The present invention relates to a bar code reader that receives the reflected light and reads the contents of the bar code.

[0002]

2. Description of the Related Art An example of a conventional bar code reader is disclosed in Japanese Patent Laid-Open Publication No. Hei 3-14190. A conventional barcode reader described in the publication will be described with reference to FIG. As shown in FIG. 1, the conventional bar code reader includes a light source 1, reflection mirrors 2 and 3 for deflecting the path of the light source 1, and a high-speed rotating mirror (polygon mirror) 4 for generating scanning light. , A light receiving lens 5 for receiving the returned light, and a light receiving element 6 for converting the light amount into an electric signal. A detection barcode 8 is provided inside the housing 7 and at a position where the polygon mirror 4 can scan the barcode. In such a configuration, the bar code 9 to be read is reflected by the reflected light 41 of the mirror 4.
And the reflected light is converted into an electric signal by a light receiving element. Then, the electric signal is converted into a digital signal, and a predetermined process is performed.

In addition, the amount of return light 42 from the detection bar code 8 provided inside the housing 7 is constantly monitored,
The light receiving element control circuit 12 controls the light receiving element 6. That is, when the reflectivity of the optical system such as the light source 1 and the mirrors 2 to 4 decreases, the light amount of the return light 42 from the detection bar code 8 attenuates, and the light receiving element control circuit 12 controls the light receiving element 6 so that the signal level becomes To return to the reference level.

Another example of a conventional bar code reader is described in Japanese Patent Application Laid-Open No. Hei 6-231290. In this publication, a filter circuit and a gain circuit of an optical circuit in a bar code reader have a plurality of shaping characteristics, and a light receiving signal is shaped and output using one of the shaping characteristics. The shaping characteristics of the filter circuit and the gain circuit
It is changed by the gain switching circuit so as to match the shape characteristics of the barcode to be detected.

[0005]

In the above-mentioned conventional bar code reading apparatus, the apparatus described in Japanese Patent Application Laid-Open No. 3-14190 receives light by returning light from a bar code label inside a housing. Controls the device. For this reason, there is a drawback that the reading rate decreases unless the barcode label actually used maintains the same quality as the barcode label inside the housing.

[0006] Also, in the device described in JP-A-6-231290, a signal is shaped and output based on the reflected light from a barcode label. For this reason, when the power of the laser beam falls below a certain output, the signal level of the bar code decreases, and there is a disadvantage that it is difficult to distinguish it from noise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and has as its object to constantly monitor the fluctuation or attenuation of the light amount (power) of a laser beam and keep the signal level at or above a certain output. It is an object of the present invention to provide a bar code reader capable of performing the above.

[0008]

A bar code reader according to the present invention irradiates an output light from a light source onto a bar code,
A bar code reading device for receiving the reflected light with a first light receiving element and reading the contents of a bar code, comprising a second light receiving element for receiving light for irradiating the bar code, It is characterized by including control means for changing the amount of the output light according to the amount of light received by the element. The control means controls the light amount of the output light to increase when the light amount received by the second light receiving element falls below a predetermined first level.

When the amount of received light is lower than a second level lower than the first level, an alarm prompting replacement of the light source is output, and the amplification factor of the output level of the first light receiving element is changed. Control to increase.

Further, first and second comparing means are provided corresponding to the first and second levels, respectively, and the corresponding levels are compared with the received light quantity, respectively. It is assumed that the second light receiving element receives light reflected from the light source by a polygon mirror.

In short, according to the present invention, a light receiving element for converting the amount of light applied to a bar code into an electric signal is provided, and the amount of laser light is constantly monitored. The light quantity converted by the light receiving element is converted into an electric signal, and the electric signal is sent to a comparison circuit and compared with a predetermined reference level. An appropriate correction value is determined by the CPU according to the comparison result of the comparison circuit,
The light amount of the laser beam is corrected by the correction value. By doing so, even when the amount of laser light fluctuates or attenuates, gain control of the signal level of the bar code can be performed, and the signal level can always be maintained at a constant output or higher.

[0012]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings referred to in the following description, the same parts as those in the other drawings are denoted by the same reference numerals.

FIG. 1 is a schematic configuration diagram showing an embodiment of a bar code reader according to the present invention, and FIG. 2 is a top view thereof. In FIG. 1, the bar code reader according to the present embodiment includes a light source 1, folding mirrors 2-1 and 2-2 for reflecting a laser beam output from the light source 1, a high-speed rotating polygon mirror (polygon mirror) 4, and It includes pattern mirrors 4a and 4b, a condenser lens 10 for condensing light reflected from the bar code 9, and a light receiving element 11 for receiving light reflected from the bar code 9. The light receiving element 11
It is configured using a photodiode or the like as a photoelectric conversion element, and converts a received light amount level into an electric signal and outputs the electric signal. This light reception output signal is input to the light reception level control circuit 80 and amplified by a video amplifier inside the light reception level control circuit 80. After being further converted into a digital signal, it is processed as a barcode signal by a digital circuit (not shown).

Further, the present apparatus is configured to include a light receiving element 50 which receives the reflected light from the polygon mirror 4 and converts the amount of light (power) into an electric signal. The light receiving element 50 is also formed using a photodiode or the like, and converts a received light amount level into an electric signal and outputs the electric signal. This light reception output signal is input to the comparison circuit 60 and compared with a predetermined reference level as described later. The comparison result of the comparison circuit 60 is input to the CPU 70, and the CPU 70
Thus, the light source output control circuit 12, the alarm lamp 13, and the light receiving level control circuit 80 are controlled.

In the bar code reader having such a configuration, the laser light emitted from the light source 1 passes through the return mirrors 2-1 and 2-2, the high-speed rotating mirror (polygon mirror) 4, and the pattern mirrors 4a and 4b. The bar code label 9 is irradiated as scanning light. Barcode label 9
Is reflected by the condenser lens 10 via the pattern mirrors 4a and 4b and the high-speed rotating mirror (polygon mirror) 4, and is received by the light receiving element 11. The output of the light receiving element 11 is amplified by a video amplifier inside the light receiving level control circuit 80, converted into a digital signal, and then processed as a bar code signal by a digital circuit (not shown). Thus, the bar code label is read.

Here, when the light amount of the laser light emitted from the light source 1 fluctuates due to the effect of temperature change or when the light amount is attenuated due to the life of the light source, the light amount from the bar code label 9 decreases and the signal level decreases. descend. In this device,
Since the light receiving element 50 for converting the light amount (power) into an electric signal is provided, the laser light reflected from the polygon mirror 4, that is, the light amount applied to the bar code can be constantly monitored.

The amount of light (power) received by the light receiving element 50
Is converted into an electric signal and sent to the comparison circuit 60. The comparison circuit 60, as shown in FIG.
Comparators 6a and 6b correspond to the output signals of the light receiving element 50 and the reference level 6 respectively.
1 and 62 are compared respectively.

Here, examples of the reference levels 61 and 62 will be described. Normally, the power of the light source decreases by 10% through one mirror. Therefore,
In the present apparatus, since three mirrors (mirrors 2-1 and 2-2 and polygon mirror 4) are interposed between the light source 1 and the light receiving element 50, the power is reduced by 30. Therefore, when the specified light amount of the light source 1 is 10 [mW], the light amount received by the light receiving element 50 is 10 × 0.7 = 7.
[MW].

In the CPU 70 of the present embodiment, three correction values are set in the light source output control circuit 12. Then, for example, the first stage has no correction until the light intensity of the light source is reduced by 30%, and the second stage has 40% to 60% of the light intensity of the light source
It is assumed that there is a correction with a small correction value until the reduction, and that the third stage has a correction with a large correction value until the specified light amount of the light source is reduced by 70% to 90%.
Then, in this case, 7 [m
W] is 3 [m], which is the reference level 61 and 70% reduction of the specified light quantity
W] becomes the reference level 62.

By setting the reference level in this way, if the light amount of the light source is larger than the reference levels 61 and 62, none of the comparators 6a and 6b of the comparison circuit 60 output a signal. The CPU 70 does not correct the light source output control circuit 12 at all. If the light amount of the light source is smaller than the reference level 61 and larger than the reference level 62, a signal is output from the comparator 6a and not output from the comparator 6b. This allows the CPU
70 performs the correction of the small correction value to the light source output control circuit 12. Furthermore, the light amount of the light source is changed to the reference levels 61 and 6
If it is smaller than 2, the comparator 6 of the comparison circuit 60
Both a and 6b output signals. Thereby, the CPU 7
A value of 0 performs a correction of a large correction value to the light source output control circuit 12. As described above, the CPU 70 can appropriately correct the light source output control circuit 12 according to the output of the comparison circuit 60.

In this embodiment, the light source output control circuit 12 is controlled based on two reference levels. However, the present invention is not limited to this. 12 can be controlled. In this case, the comparison circuit 60 is configured using the number of comparators corresponding to each reference level, and the output of each comparator is
What is necessary is just to input to U70 and control.

Returning to FIG. 1, based on the electric signals output from the comparators 6a and 6b in the comparison circuit 60, the CP
In U 70, an appropriate correction value is determined and sent to the light receiving level control circuit 80. Thereby, the gain of the video amplifier (not shown) in the light receiving level control circuit 80 is controlled. Therefore, even when the light amount (power) of the laser beam fluctuates or attenuates, the gain control of the signal level of the bar code can be performed, and the signal level can always be maintained at a certain level or more.

When the light amount falls to the lowest level due to the life of the light source 1 and the like, and the light source output control circuit 12 cannot control the output of the light source 1, the CPU 70 turns on the alarm lamp 13 or emits an alarm. Output to prompt replacement of the light source 1. Instead of turning on the alarm lamp 13,
A buzzer may be sounded, or these may be used in combination.

Further, the CPU 70 switches the transmission destination of the control signal from the light source output control circuit 12 to the light receiving level 80 at the same time as outputting the alarm. Even in this case,
A correction value is determined in the CPU 70 according to the signal sent from the light receiving element 50 to the comparison circuit 60, and the light receiving level control circuit 80 is controlled. As a result, even when the light amount of the light source 1 falls to the lowest level, gain control of the signal level of the bar code can be performed, and normal reading processing can be performed until the light source is replaced.

[0025]

As described above, according to the present invention, by constantly monitoring the amount of laser light and determining an appropriate correction value,
Even when the amount of laser light fluctuates or attenuates, gain control of the barcode signal can be performed, and the signal level can always be maintained at a certain level or higher.

Also, by constantly monitoring the amount of laser light, even if the amount of light is attenuated over the life of the light source,
By making corrections, you can keep the signal level above a certain level,
There is an effect that the life of the light source can be maximized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a configuration of a barcode reading device according to an embodiment of the present invention.

FIG. 2 is a top view illustrating a configuration of the barcode reading device of FIG. 1;

FIG. 3 is a block diagram illustrating a configuration example of a comparison circuit in FIG. 1;

FIG. 4 is a schematic configuration diagram showing a configuration example of a conventional barcode reading device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light source 2-1 and 2-2 Folding mirror 3 High-speed rotating mirror 4a, 4b Pattern mirror 11, 50 Light receiving element 9 Barcode label 10 Condensing lens 11 Light receiving element 12 Light source output control circuit 13 Alarm lamp 14 Reflecting mirror 60 Comparison circuit 70 CPU 80 Light receiving level control circuit

Claims (6)

[Claims] 1. A bar code reading device for irradiating an output light from a light source to a bar code and receiving the reflected light with a first light receiving element to read the contents of the bar code, and irradiates the bar code. A second light receiving element for receiving light;
A bar code reader comprising a control means for changing the amount of the output light in accordance with the amount of light received by the second light receiving element. 2. The method according to claim 1, wherein the control unit controls the light amount of the output light to increase when the light amount received by the second light receiving element falls below a predetermined first level. The barcode reader according to claim 1. 3. The apparatus according to claim 2, further comprising an alarm output unit that outputs an alarm prompting replacement of the light source when the amount of received light is lower than a second level lower than the first level. The bar code reader according to the above. 4. A light-receiving level control circuit for controlling an amplification factor of an output level of the first light-receiving element to increase when the amount of received light falls below a second level lower than the first level. 3. The method according to claim 2, further comprising:
Or the barcode reader according to 3. 5. The apparatus according to claim 1, further comprising first and second comparing means provided corresponding to the first and second levels, respectively, for comparing the corresponding level with the received light amount. Item 5. The barcode reader according to any one of Items 1 to 4. 6. The bar code reading device according to claim 1, wherein the second light receiving element receives light reflected by a polygon mirror of output light from the light source.