JP3194631B2 - Barcode reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a bar code reader, and more particularly to a structure for outputting bar code data based on an accurate bar code waveform.

[0002]

2. Description of the Related Art FIG. 8 schematically shows a conventional bar code reader.
It will be described based on. The bar code reader is provided with a semiconductor laser 41, and the semiconductor laser 41 emits a laser beam L1. The laser light L1 passes through the collimator lens 42 and is reflected on the reflection surface 4 of the polygon mirror 43.
It is incident on 3M. Then, the laser beam L1 is further reflected by the reflection surface 43M to form an irradiation spot S1 on the barcode 10.

A bar code is composed of bars and spaces having different thicknesses, and predetermined bar code data is represented according to a combination of these bars and spaces. Barcode 1
The irradiation spot S1 formed on the scanning line 0 is scanned on the scanning line W1 from the irradiation position P1 to P2. In order to scan the irradiation spot S1, the polygon mirror 43 rotates at a high speed. That is, the polygon mirror 43 shown in the figure is a hexahedron having six reflection surfaces 43M, and rotates in the direction of the arrow 90 around the rotation axis 43J. The rotation of the polygon mirror 43 changes the angle of the reflection surface 43M.

In accordance with the change in the angle of the reflection surface 43M, the irradiation spot S1 moves and scans on the scanning line W1 from the irradiation positions P1 to P2 in the direction of the arrow 91.
Then, when the laser light L1 from the semiconductor laser 41 is incident on the next reflection surface 43M due to the rotation of the polygon mirror 43, the irradiation spot S1 is formed again at the irradiation position P1, and again according to the angle change of the reflection surface 43M. , The scanning up to the irradiation position P2 is repeated.

[0005] A reflected laser beam L2 of the laser beam L1 is generated from the bar code 10 on which the irradiation spot S1 is formed. The reflected laser beam L2 is condensed by the condenser lens 44 and received by the light receiving section 8. Then, the light receiving section 8 outputs a received light waveform signal, and barcode data is recognized based on the received light waveform signal. That is, in the bar code 10, the black portion of the bar absorbs the received light, and the white portion of the space diffusely reflects the light. For this reason, the reflected laser light L2 is generated with the intensity corresponding to the barcode 10, and the barcode data can be recognized based on the received light waveform signal.

A circuit configuration for detecting bar code data will be described with reference to the block diagram of FIG. The received light waveform signal from the light receiving section 8 is first amplified by the preamplifier circuit 51. FIG. 7A shows the amplified received light waveform signal. As described above, the irradiation spot S1 of the laser beam L1 is repeatedly scanned on the scanning line W1. For this reason, a light-receiving waveform signal corresponding to this will be formed by repeating the same waveform.

In the waveform shown in FIG. 7A, the bar code waveform signal K1 is the read waveform of the bar code 10, and FIG. 7B is a partially enlarged view of the bar code waveform signal K1.
Such a received light waveform signal is supplied from the preamplifier circuit 51 to the high-pass filter 52 (see FIG. 5), where the low-frequency component is removed. That is, since only the barcode waveform signal K1 necessary for reading barcode data is extracted, other low-frequency component waveforms (see FIG. 7A)
To cut.

FIG. 6 shows the frequency characteristics of the high-pass filter 52.
Is shown in the graph. The horizontal axis of the graph is frequency, and the vertical axis is gain. As shown in FIG.
Removes low waveform signals and outputs only high frequency components. The received light waveform signal is shaped by the high-pass filter 52 having such characteristics, and only a waveform signal of a high frequency component can be obtained. FIG. 7C shows a partially enlarged view of the barcode waveform signal output from the high-pass filter 52.

The light-receiving waveform signal from the high-pass filter 52 is applied to a delay attenuation circuit 53 shown in FIG. The delay attenuation circuit 53 delays and attenuates the received light waveform signal. Then, the comparison circuit 54 (FIG. 5) fetches the delayed attenuation waveform signal and the light reception waveform signal from the high-pass filter 52, compares them, and superimposes the waveforms. FIG. 7D shows the delayed attenuation waveform signal H2 and the light reception waveform signal H1. In this way, the delay attenuation waveform signal H2 is compared with the light reception waveform signal H1, and barcode data is output based on the intersection of both waveforms as shown in FIG. 7E.

[0010]

The above-mentioned conventional bar code reader has the following problems. The light-receiving waveform signal (FIG. 7C) that has passed through the high-pass filter 52 is applied as it is to the delay attenuation circuit, where the signal is delayed and attenuated. Then, the received light waveform signal and the delayed attenuation waveform signal are compared, and barcode data is output (see FIG. 7D).

Therefore, when the received light waveform signal output from the high-pass filter is distorted, there is a problem that barcode data cannot be accurately recognized. Particularly, the high-pass filter 52 has a frequency characteristic as shown in FIG. 6 as described above. For this reason, even low-frequency components included in the received light waveform signal itself are removed, and distortion occurs in the shaped waveform signal (see FIGS. 7B and 7C). That is, since barcode data is output based on such a shaped waveform signal, barcode data cannot be recognized accurately.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bar code reader having a high reading accuracy and capable of outputting appropriate bar code data based on an accurate waveform signal.

[0013]

According to a first aspect of the present invention, there is provided a bar code reader which emits light toward a bar code, receives light reflected from the light, and includes a bar code waveform signal. A light receiving unit that outputs a signal, a center line calculating unit that calculates a center line of the bar code waveform signal, and aligns the center of the bar code waveform signal based on the center line;
Shaping means for generating a shaped barcode waveform signal, a delayed attenuated waveform signal generating means for delaying the shaped barcode waveform signal, and attenuating the amplitude of the shaped barcode waveform signal to generate a delayed attenuated waveform signal, and the shaped barcode Data output means for comparing the waveform signal with the delayed attenuation waveform signal and outputting barcode data based on the intersection of the waveform signal and the delayed attenuation waveform signal.

According to a second aspect of the present invention, in the bar code reading apparatus according to the first aspect, the shaping means aligns the center of the bar code waveform signal based on the center line and outputs the bar code waveform signal. It is characterized in that a shaped barcode waveform signal is generated by unifying the amplitude.

According to a third aspect of the present invention, in the bar code reader according to the first aspect, the scanning means for repeatedly scanning the light emitted from the light emitting section toward the bar code, and the waveform signal. A repetitive waveform signal removing means for receiving the received light waveform signal from the generating means and removing only the received light waveform signal repeatedly generated in accordance with the scanning of the scanning means.

[0016]

In the bar code reader according to the first aspect, the center line calculating means calculates the center line of the bar code waveform signal, and the shaping means aligns and shapes the center of the bar code waveform signal based on the center line. Generate a barcode waveform signal. Then, the delay attenuation waveform signal generating means includes:
The shaped barcode waveform signal is delayed, and the amplitude of the shaped barcode waveform signal is attenuated to generate a delayed attenuated waveform signal, and the data output means outputs barcode data.

Therefore, barcode data can be output based on a correctly shaped barcode waveform signal with a uniform center.

In the bar code reader according to the second aspect, the shaping means aligns the center of the bar code waveform signal based on the center line and unifies the amplitude of the bar code waveform signal to convert the shaped bar code waveform signal. Generate.

Therefore, when the delayed attenuated waveform signal is generated by the delayed attenuated waveform signal generating means, it is possible to avoid an error in the delayed attenuated waveform signal caused by the inconsistency of the amplitude of the barcode waveform signal.

In the bar code reader according to the third aspect, the scanning means repeatedly scans the bar code with the irradiation light emitted from the light emitting section. Then, the repetitive waveform signal removing means takes in the received light waveform signal from the waveform signal generating means and removes only the received light waveform signal repeatedly generated by the scanning of the scanning means.

Therefore, it is possible to eliminate a light receiving waveform signal unnecessary for outputting bar code data while maintaining an accurate bar code waveform signal.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bar code reader according to the present invention will be described with reference to the drawings. The bar code reader irradiates laser light as irradiation light from a semiconductor laser. The polygon mirror serving as the scanning means reflects this laser light while rotating at high speed, and scans the laser light on the bar code (see FIG. 8). On the other hand, the reflected light from the bar code is received by the light receiving unit, and a light receiving waveform signal is output. Since the reflected light is generated depending on the intensity of the bar code, bar code data can be output based on the received light waveform signal.

An embodiment of a circuit configuration for outputting bar code data is shown in the block diagram of FIG. The light receiving section 8 that has received the reflected light from the bar code outputs a received light waveform signal, and the received light waveform signal is amplified by the preamplifier circuit 3.
FIG. 4A shows the amplified received light waveform signal. The light receiving waveform signal includes a bar code waveform signal K5 which is a bar code reading portion. FIG. 4B is a partially enlarged view of the barcode waveform signal K5. Since the laser light is repeatedly scanned on the bar code as described above, the light receiving waveform signal shown in FIG. 4A is also formed as a repetition of the same waveform.

The light-receiving waveform signal having passed through the preamplifier circuit 3 is then taken into a repetitive component removing circuit 5. The repetitive component removing circuit 5 removes only the light-receiving waveform signal that is repeatedly generated in accordance with the scanning of the laser beam. That is, the light reception waveform signals other than the barcode waveform signal K5 in the waveform of FIG. 4A are cut. Here, when the frequency of the received light waveform signal other than the barcode waveform signal K5 is fa,
FIG. 3 shows the frequency characteristics of the repetitive component removing circuit 5. As shown in the figure, the repetitive component removing circuit 5 removes only a specific frequency component fa, that is, only a light receiving waveform signal other than the barcode waveform signal K5.

FIG. 4C shows a received light waveform signal output from the repetitive component removing circuit 5, and FIG. 4D shows a partially enlarged view of the bar code waveform signal K6 in the received light waveform signal. Since only the repetitive component is removed and the low-frequency component of the barcode waveform signal K6 itself is maintained, distortion of the waveform signal can be suppressed.

The light-receiving waveform signals shown in FIGS. 4C and 4D are supplied to a peak envelope generation circuit 15 and a bottom envelope generation circuit 17 via a subtraction circuit 7 and an automatic gain control circuit 9. The peak envelope generation circuit 15 calculates a peak waveform G1 (FIG. 4D) of the received light waveform signal, and the bottom envelope generation circuit 17 calculates a bottom waveform G2 (FIG. 4D) of the received light waveform signal.

The peak waveform G1 and the bottom waveform G2 are taken into the midpoint potential detection circuit 19, and a center waveform signal (FIG. 4D) as a center line is calculated and detected based on the peak waveform G1 and the bottom waveform G2. You. FIG. 2 shows one embodiment of the peak envelope generating circuit 15, the bottom envelope generating circuit 17, and the midpoint potential detecting circuit 19.

The center waveform signal G9 is supplied to the midpoint potential detection circuit 19.
From the received light waveform signal (FIG. 4).
Feedback on C, D) is provided. That is, the center waveform signal G9 is subtracted from the received light waveform signal, and the center of the barcode waveform signal K6 is aligned. Also, the bottom waveform G2 from the bottom envelope generation circuit 17
Is also given to the automatic gain control circuit 9. Then, based on the bottom waveform G2, feedback for keeping the amplitude of the light receiving waveform signal (FIGS. 4C and D) constant is performed. As described above, the centering of the barcode waveform signal K6 is performed, and the amplitude of the waveform is shaped to be constant, thereby generating a shaped barcode waveform signal. Next, the shaped barcode waveform signal is applied to the delay subtraction circuit 11. The delay attenuation circuit 11 delays and attenuates the shaped barcode waveform signal to generate a delayed attenuation waveform signal.

Then, the comparison circuit 13 takes in the delayed attenuation waveform signal and the shaped barcode waveform signal, compares them, and superimposes the waveforms. FIG. 4E shows the shaped barcode waveform signal H5 and the delayed attenuation waveform signal H6. Thus, the shaped barcode waveform signal H5 and the delayed attenuation waveform signal H6
And outputs barcode data based on the intersection of both waveforms as shown in FIG. 4F.

As described above, in this embodiment, only the repetitive component in the received light waveform signal is removed by the repetitive component removing circuit 5, and the center and the amplitude of the bar code waveform signal K6 (FIG. 4) are made uniform. Thus, a shaped barcode waveform signal is generated. Then, a delay attenuation process is performed based on such a shaped barcode waveform signal, and barcode data is recognized, so that accurate barcode reading becomes possible.

In the present embodiment, the automatic gain control circuit 9 performs feedback for keeping the amplitude of the received light waveform signal constant based on the bottom waveform from the bottom envelope generation circuit 17, but the peak envelope generation circuit The feedback may be performed based on the peak waveform from 15. Also, feedback based on the difference between the bottom waveform and the peak waveform can be performed. in this case,
A subtraction circuit for calculating the difference between the two is provided.

[0032]

In the bar code reader according to the first aspect, the center line calculating means calculates the center line of the bar code waveform signal, and the shaping means determines the center of the bar code waveform signal based on the center line. Generate an alignment shaping barcode waveform signal. The delayed attenuated waveform signal generating means delays the shaped barcode waveform signal and attenuates the amplitude of the shaped barcode waveform signal to generate a delayed attenuated waveform signal, and the data output means outputs barcode data.

That is, it is possible to output barcode data based on an accurate shaped barcode waveform signal having a uniform center.

Therefore, it is possible to provide a bar code reader having high reading accuracy.

In the bar code reading apparatus according to the second aspect, the shaping means aligns the center of the bar code waveform signal based on the center line and unifies the amplitude of the bar code waveform signal to convert the shaped bar code waveform signal. Generate.

That is, when the delayed attenuated waveform signal generating means generates the delayed attenuated waveform signal, it is possible to avoid an error in the delayed attenuated waveform signal caused by the inconsistency of the amplitude of the barcode waveform signal.

Therefore, more accurate bar code data can be output.

In the bar code reading device according to the third aspect, the scanning means repeatedly scans the irradiation light emitted from the light emitting section toward the bar code. Then, the repetitive waveform signal removing means takes in the received light waveform signal from the waveform signal generating means and removes only the received light waveform signal repeatedly generated by the scanning of the scanning means.

That is, while maintaining an accurate bar code waveform signal, it is possible to eliminate a light receiving waveform signal unnecessary for outputting bar code data.

Therefore, more accurate bar code data can be output.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration in an embodiment of a barcode reader according to the present invention.

FIG. 2 is a circuit diagram of a peak envelope generation circuit, a bottom envelope generation circuit, and a midpoint potential detection circuit shown in FIG.

FIG. 3 is a diagram illustrating a frequency characteristic of the repetitive component removing circuit illustrated in FIG. 1;

FIG. 4 is a diagram showing a waveform of an output signal output from each circuit shown in FIG. 1;

FIG. 5 is a block diagram showing a circuit configuration of a conventional barcode reading device.

FIG. 6 is a diagram illustrating frequency characteristics of the bypass filter illustrated in FIG. 5;

FIG. 7 is a diagram showing a waveform of an output signal output from each circuit shown in FIG. 5;

FIG. 8 is a perspective view for explaining the outline of a barcode reading device.

[Explanation of symbols]

 3 ····························································································· Automatic gain control circuit 11 ··· ..Delayed subtraction circuit 13 ... Comparison circuit 15 ... Peak envelope generation circuit 17 ... Bottom envelope generation circuit 19 ... Middle point potential detection circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-65585 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06K 7/10 G06K 7/00

Claims (3)

(57) [Claims] A light-emitting unit for irradiating irradiation light toward a bar code; a light-receiving unit for receiving reflected light of the irradiation light and outputting a light reception waveform signal including a bar code waveform signal; a center line of the bar code waveform signal , A shaping means for aligning the center of the barcode waveform signal based on the center line and generating a shaped barcode waveform signal, delaying the shaped barcode waveform signal, and amplitude of the shaped barcode waveform signal A delayed attenuated waveform signal generating means for generating a delayed attenuated waveform signal by attenuating the data, a data output means for comparing the shaped barcode waveform signal and the delayed attenuated waveform signal, and outputting barcode data based on an intersection of the two. A bar code reader comprising: 2. The bar code reader according to claim 1, wherein said shaping means aligns the center of the bar code waveform signal based on a center line and unifies the amplitude of the bar code waveform signal to form the bar code waveform signal. A bar code reader for generating a signal. 3. The bar code reading device according to claim 1, wherein: scanning means for repeatedly scanning the irradiation light emitted from the light emitting unit toward the bar code; and receiving a light reception waveform signal from the waveform signal generation means. ,
A bar code reader comprising: a repetitive waveform signal removing unit that removes only a received light waveform signal that is repeatedly generated according to scanning by the scanning unit.