JP3104455B2 - Optical information reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information reading apparatus for reading optical information from a reading object on which optical information such as a bar code is described.

[0002]

2. Description of the Related Art Conventionally, as an optical information reading apparatus for reading optical information such as a bar code, a laser beam emitted from a laser light source 62 is collimated by a collimating lens 64 as shown in FIG. A bar code label 70 on which a bar code is printed is scanned by irradiating a scan mirror 68 which is reciprocated in the direction of the arrow shown in the figure by a stepping motor 66, and the bar code label 70 is reflected by the scan. The reflected light is reflected again by the scan mirror 68, and the condensing lens 7
An optical system configured to guide an electric signal corresponding to the amount of received light to a photodetector 74 through the optical detector 7;
Amplifying circuit 76 for amplifying a weak electric signal output from 4 to a required level, a binarizing circuit 78 for binarizing the signal amplified by the amplifying circuit 76, and a binary output from the binarizing circuit 78 Counting section 80 that determines the narrow bar and wide bar of the bar code by counting the width of the coded signal, and decodes the bar code based on the output signal from the counting section 80, and outputs the decoding result to an output terminal 82a. Decoding section 82 which outputs to the outside through
, A driving system including a mirror driving circuit 84 for driving the stepping motor 66, a laser driving circuit 86 for driving the laser light source 62, and the like, and a laser beam from the laser light source 62 via the laser driving circuit 86. , And drives a stepping motor 66 via a mirror driving circuit 84 to control the scanning mirror 68 to reciprocate at a predetermined cycle (about 50 Hz). Device 60
It has been known.

Generally, the counting section 80, the decoding section 82, and the control section 88 are realized as one process of an electronic control unit (ECU) composed of a microcomputer mainly including a CPU, a ROM, a RAM, and the like.

[0004]

In such a conventional bar code reader, a bar code is applied to a member having a large regular reflection component when irradiated with light, such as glossy high-quality paper, vinyl, glass or the like. If printed, the photodetector receives the light (specular reflection component) due to specular reflection from the member on which the barcode is printed, depending on the angle at which the light is illuminated. There was something I could not do. When reading fails due to the effect of specular reflection, the reading angle is changed and the reading is attempted again so as not to be affected by the specular reflection.However, the reading may fail many times. Also, there is a problem that the usability of the barcode reader is greatly impaired.

SUMMARY OF THE INVENTION The present invention provides an optical information reading apparatus capable of reliably reading optical information without being affected by specular reflection in the reading of optical information. The purpose is to provide.

[0006]

According to a first aspect of the present invention, there is provided a light source for irradiating a reading target on which optical information is described with light, as shown in FIG. Means, light receiving means for receiving reflected light reflected from the object to be read, and outputting a light receiving signal corresponding to the received reflected light, and reading means for reading the optical information from the light receiving signal from the light receiving means And a plurality of the light receiving means are arranged at different positions from each other, and for each of the light receiving signals from each of the light receiving means, the light receiving signal causes specular reflection of the object to be read. Specular reflection determining means for determining whether or not the light receiving signal has been influenced by the specular reflection, and one of the light receiving signals determined not to be affected by the specular reflection by the specular reflection determining means is selectively applied to the reading means. Signal selection And means, the optical information reading apparatus comprising the have the gist.

[0007] The invention described in claim 2 is the first invention.
In the optical information reading device according to the above, the specular reflection determining means integrates the light receiving signal for each light receiving signal from each of the light receiving means, and further applies a predetermined voltage to the integrated light receiving signal to thereby obtain a mirror surface reflection. A reference voltage setting means for setting a reference voltage for reflection determination; and comparing the magnitude of the reference voltage set by the reference voltage setting means with the light receiving signal, and when the light receiving signal is larger than the reference voltage, the light receiving signal Is a gist of an optical information reading device comprising: a determination unit for determining that the optical information reading device is affected by specular reflection.

[0008]

In the optical information reading apparatus according to the first aspect of the present invention, the light source irradiates light to the object to be read on which the optical information is written, and the light receiving means irradiates the light with the light. Receives reflected light reflected from the object to be read,
The light receiving signal corresponding to the reflected light is output. Further, a plurality of light receiving means are provided at different positions from each other, and the specular reflection determining means determines, for each light receiving signal output from the plurality of light receiving means, whether or not the light receiving signal is affected by specular reflection. judge. Then, according to the determination result, the signal selecting means selects one light receiving signal from the light receiving signals not affected by the specular reflection and inputs the signal to the reading means. The reading means reads optical information from the selected light receiving signal.

According to the optical information reading apparatus of the present invention, the reference voltage set by integrating the light receiving signal by the reference voltage setting means and further applying a predetermined voltage together with the light receiving signal is determined by the determining means. To determine whether the light receiving signal is affected by specular reflection by comparing the light receiving signal with the reference voltage.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram illustrating a configuration of an entire barcode reading device according to an embodiment to which the present invention is applied.

As shown in FIG. 1, a bar code reader 1 according to the present embodiment is a portable device, and has a grip portion 1a formed at a lower portion of a main body. The optical system is provided on the upper part of the main body, and has a laser light source 2 for generating a laser beam and a laser light source 2 similar to the bar code reader of FIG.
A collimating lens 4 for converting the laser beam from the collimating beam into a parallel beam, a scan mirror 8 for scanning the laser beam transmitted through the collimating lens 4 to irradiate a barcode label 6 on which a barcode is printed, Two photodetectors 10 as light receiving means for generating an electric signal corresponding to the amount of light (that is, a difference in reflectance between a bar portion and a space portion of a bar code appears as a magnitude of a voltage of the electric signal).
a, 10b, and a condensing lens 12 for condensing laser light (scattered light) reflected from the bar code label 6 and further reflected on the scan mirror 8 to each of the photodetectors 10a, 10b.
a and 12b.

The scanning mirror 8 is a stepping motor 1 that reciprocates at a predetermined cycle (for example, 50 Hz).
4 is attached to the rotating shaft. Also, the photodetectors 10a, 1
Reference numeral 0b is disposed at a position apart from each other in the barcode reader 1, and the condenser lenses 12a and 12b are also disposed on the corresponding optical path.

Next, the signal processing system of the bar code reader 1 of this embodiment is formed on a circuit board 16 and corresponds to each of the photodetectors 10a and 10b.
Amplifying circuits 18a and 18b for amplifying a weak electric signal output from the amplifier to a required magnitude, and amplifying circuits 18a and 18b
a binary signal having a built-in specular reflection determination circuit as specular reflection determination means for determining whether the received light signal is affected by specular reflection and outputting a determination signal while binarizing the received light signal amplified by b. Circuit 20a, 20b.

In this signal processing system, each binarizing circuit 2
A signal selection circuit 22 for selectively outputting either one of the binarized signals inputted from 0a and 20b, and monitoring a judgment signal from a specular reflection judgment circuit built in each of the binarization circuits 20a and 20b. A signal selection control unit 24 that selects a binary signal to be output from the signal selection circuit 22 based on the determination result and controls the signal selection circuit 22 to output the selected binary signal; A counting unit 26 that determines the narrow bar and the wide bar of the bar code by counting the width of the binarized signal output from the unit 22; and decodes (decodes) the bar code based on the output signal from the counting unit 26. A decoding unit 28 that outputs the decoding result to an external device via an output terminal 28a is provided.

The signal selection control unit 24 and the counting unit 2
6 and the decoding unit 28 are realized as one process of an electronic control unit (ECU) including a microcomputer mainly including a CPU, a ROM, a RAM, and the like. On the other hand, the drive system of the barcode reader 1 of the present embodiment includes a mirror drive circuit 30 for driving the scan mirror 8 by the stepping motor 14 and a laser drive circuit 3 for driving the laser light source 2.
And the control system is a mirror driving circuit 3
0, a control unit 34 that controls the operations of the laser drive circuit 32 and the decoding unit 28 and is implemented as one process of the ECU. A power supply 36 for supplying power to the above-described units is housed inside the grip unit 1a formed below the main body of the barcode reader 1.

Next, the binarization circuit 20 will be described.
FIG. 2 is an electric circuit diagram showing a configuration of a binarizing circuit 20 having a built-in specular reflection determination circuit as specular reflection means. As shown in FIG. 2, the binarization circuit 20 outputs the light receiving signal S
The integration circuit 42 composed of a resistor R1 and a capacitor C1 for integrating A is compared with the light receiving signal SA and the integrated light receiving signal (hereinafter referred to as a binarization determination threshold) SB to determine whether the light receiving signal SA is larger. Comprises a voltage comparator 40 for outputting a binary signal SC which becomes a high level when the current is large, a resistor R2 and diodes D1 and D2 connected to a power supply, and a diode generated by a current supplied from the resistor R2. A bias circuit 48 for applying a predetermined voltage to the binarization determination threshold SB using the forward voltage drop of D1 and D2
Is compared with the light receiving signal SA and a binarization determination threshold (hereinafter, “specular reflection determination threshold”) SD to which a predetermined voltage is applied. And a voltage comparator 46 for outputting the signal SE.

Next, the binarizing circuit 2 constructed as described above
The operation of 0 will be described. In FIG. 4, (A)
Represents a barcode label on which specular reflection 52 has occurred. Similarly, (B) shows the light receiving signals SA, 2 when the bar code label of (A) is scanned in the direction indicated by the arrow X.
Threshold value determination threshold SB and specular reflection determination threshold value S
The waveform of D is shown. Similarly, (C) and (D) are 2
2 shows a binarized signal SC and a determination signal SE output from the digitizing circuit 10.

As shown in FIG. 4, by scanning the bar code label, the light receiving signal SA input to the binarizing circuit 20 is converted into a binary signal obtained by integrating the light receiving signal SA in the voltage comparator 40. The magnitudes are compared based on the threshold value SB. As a result, the light receiving signal SA is binarized, and the binarization circuit 20 outputs the binarized signal SC.

At the same time, the magnitude of the light receiving signal SA is compared in the voltage comparator 46 with reference to a specular reflection judgment threshold value SD which is higher by a predetermined voltage than the binarization judgment threshold value SB. Note that the predetermined voltage is applied to the bias circuit 4.
8 can be set freely by the number of connected diodes, and is not affected by specular reflection.
The specular reflection determination threshold value SD is set to be always larger. If specular reflection occurs here,
Since light stronger than usual is detected by the photodetector 10 due to the specular reflection component, the voltage level of the portion of the light receiving signal SA input to the binarization circuit 10 that is affected by specular reflection is determined by specular reflection. It is larger than the threshold value SD.

As a result, the binarizing circuit 20 outputs a determination signal SE when the light receiving signal SA is affected by specular reflection. These series of operations are performed by the binarization circuit 20 for each of the light receiving signals SAa and SAb output from each photodetector 18.
The binarized signals SCa and SCb output from the binarization circuits 20a and 20b are input to the signal selection circuit 22, and the determination signals SEa and SEb are input to the signal selection control unit 24. .

Next, a bar code reading control process performed in the ECU will be described with reference to a flowchart shown in FIG. Since the mirror drive circuit 30 and the laser drive circuit 32 are driven after the power of the bar code reader is turned on, the laser light emitted from the laser light source 2 driven by the laser drive circuit 32 is transmitted by the mirror drive circuit 32. The scanning mirror 8 which is attached to the rotating shaft of the driven stepping motor 14 and performs reciprocating motion always performs reciprocating scanning at a predetermined cycle.

First, at step 110, it is confirmed that the mirror driving circuit 30 and the laser driving circuit 32 are normally driven and are in a state where reading is possible. Step 12
In the case of 0, the laser beam scans the barcode label 6 and the reflected light is received by the photodetectors 10a and 10b. As a result, the determination signals SEa and
Read SEb.

In step 130, it is determined whether or not the influence of specular reflection is detected based on the read determination signal SEa. If not detected, the received light signal SAa
Is determined not to be affected by specular reflection, and the flow proceeds to step 140. In step 140, the signal selection circuit 22 is controlled such that the signal SCa obtained by binarizing the light receiving signal SAa is output from the signal selection circuit 22.

In step 150, the binary signal SC output from the signal selection circuit 22 is read, and in step 16
At 0, the widths of the bars and spaces of the read binary signal SC are counted to digitize the widths of the bars and spaces. At step 170, the information of the bar code signal is restored from the digitized data, and the output terminal is output. Output from 28a to the external device ends a series of controls.

In step 130, the determination signal S
When the influence of specular reflection is detected by Ea, the process proceeds to step 180. In step 180, it is determined whether or not the influence of specular reflection is detected based on the read determination signal SEb. If not, it is determined that the light receiving signal SAb is not affected by specular reflection, and the process proceeds to step 190.

In step 190, the light receiving signal SAb is set to 2
The process proceeds to step 150 by controlling the signal selection circuit 22 so that the coded signal SCb is output from the signal selection circuit 22. The binary signal SC output from the signal selection circuit 22 is read and read. The digitized signal SC is digitized, barcode signal information is restored from the digitized data, and output to an external device to end a series of controls.

In step 180, the determination signal S
When the influence of specular reflection is detected by Eb, the process proceeds to step 200. In step 200, an error sound indicating a reading failure is generated by a buzzer (not shown) controlled by the control unit, and the series of controls is ended.

As described above, in the bar code reader 1 of the present embodiment, the light reflected from the bar code label 6 is reflected by the two photo detectors 10a and 10b arranged at different positions. Receiving light, and each photodetector 10
a, 10b, the binarization circuits 20a, 20b output the light receiving signals SAa, SAb.
It is determined whether or not b is affected by specular reflection. Then, based on the determination signals SEa and SEb output from the binarization circuits 20a and 20b, a light receiving signal that is not affected by specular reflection is selected from the two light receiving signals, and optical information is obtained from the selected light receiving signal. Has been read. When both light receiving signals are affected by specular reflection, optical information is not read from the received light signal affected by specular reflection only by generating a reading error sound.

Therefore, the reading process of the optical information is always performed using the signal which is not affected by the specular reflection, so that the optical information can be read accurately. Further, by receiving light with two photodetectors arranged at different positions from each other, it is possible to reduce the occurrence of a reading error because the possibility that both light receiving signals are simultaneously affected by specular reflection is low.

Further, in the present embodiment, in the binarization circuit 20, the light receiving signal SA and a specular reflection determination threshold SD generated by integrating the light receiving signal SA and applying a predetermined voltage.
Are compared to determine the presence or absence of the influence of specular reflection. For this reason, since the specular reflection determination threshold value SD is set according to the received light signal SA, it is possible to make a reliable determination regardless of the average level of the received light signal SA. Further, the binarization circuit 20 for making this determination is
Since no input signal is required other than the light receiving signal SA, the configuration is simple.

Although the embodiment of the present invention has been described above, the configuration of the present invention is not limited to the above-described embodiment, and the same effects as those of the above-described embodiment can be obtained in the following configuration. Obtainable. For example, in the above embodiment, the condensing lenses 12a and 12b and the photodetectors 10a and 10b are separately used, but, for example, a plurality of condensing lenses and photodetectors housed in one package. May be used.

In the above-described embodiment, the apparatus for reproducing optical information by scanning light and using the intensity of the reflected light has been described. However, the present invention can be similarly applied to an apparatus for receiving reflected light as an image by an image sensor. . In the above embodiment, two photodetectors are used. However, if the number of photodetectors is increased, a device with less reading errors can be configured.

[0033]

As described above, according to the optical information reading apparatus of the first aspect, a plurality of light receiving means arranged at different positions receive reflected light from the object to be read. It is determined whether or not each of the light-receiving signals output from is affected by specular reflection, and only one light-receiving signal that is not affected by specular reflection is selected from among these light-receiving signals. Optical information is read from the received light signal.

Therefore, the optical information reading process is always performed using a signal which is not affected by specular reflection, so that the optical information can be read accurately. Further, by receiving light with a plurality of light receiving means, it is unlikely that all light receiving signals are simultaneously affected by specular reflection, so that the occurrence of reading errors can be reduced.

Also, in the optical information reading apparatus according to the present invention, the light receiving signal output from the light receiving means is integrated, and a predetermined voltage is applied to the integrated light receiving signal to thereby determine the specular reflection. A voltage is generated, and the presence or absence of the influence of specular reflection is determined by comparing the reference voltage with a light receiving signal output from the light receiving means.

For this reason, since the reference voltage is set according to the received light signal, it is possible to reliably determine whether or not there is an influence of specular reflection regardless of the average level of the received light signal.
Further, since this determination does not require any signal other than the light receiving signal, the configuration of the specular reflection determining means can be simplified.

[Brief description of the drawings]

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

FIG. 2 is an electric circuit diagram illustrating a configuration of a binarization circuit according to the present embodiment.

FIG. 3 is an explanatory diagram illustrating an operation of the binarization circuit according to an input / output signal of the binarization circuit in the embodiment.

FIG. 4 is a flowchart illustrating a barcode reading control process performed in an ECU according to the present embodiment.

FIG. 5 is a schematic configuration diagram illustrating an entire configuration of a conventional barcode reading device.

[Explanation of symbols]

1. Barcode reader 2. Laser
4: Collimator lens 6: Bar code label 8: Scan mirror 1
0: Photodetector 12: Condensing lens 14: Stepping motor

Claims (2)

(57) [Claims] 1. A light source unit for irradiating light to a reading target on which optical information is described, receiving reflected light reflected from the reading target, and outputting a light receiving signal corresponding to the received reflected light. An optical information reading device comprising: a light receiving means; and a reading means for reading the optical information from the light receiving signal from the light receiving means, wherein a plurality of the light receiving means are provided at different positions from each other; A specular reflection determining unit that determines whether or not the light receiving signal is affected by the specular reflection of the object to be read, and the specular reflection determining unit determines the influence of the specular reflection. An optical information reading apparatus, comprising: signal selecting means for selectively inputting one of the light receiving signals determined not to have been received to the reading means. 2. The optical information reading device according to claim 1, wherein the specular reflection determining means integrates the light receiving signal for each light receiving signal from each of the light receiving means, and further includes the integrated light receiving signal. Reference voltage setting means for setting a reference voltage for specular reflection determination by applying a predetermined voltage to the reference voltage; comparing the magnitude of the reference voltage set by the reference voltage setting means with the light receiving signal; Determining means for determining that the received light signal is affected by specular reflection when the voltage is higher than the voltage;