JPH0620080A - Bar code read scanner - Google Patents

Abstract

(57) [Summary] [Purpose] To ensure that the barcode label can be read even if it is uneven or dirty. A bar code reading scanner that irradiates a bar code label with a light beam from a laser diode 5 and photoelectrically converts the reflected light by a photodiode 6 to obtain a decoding signal. The sub-scanning drive unit 13 performs sub-scanning in a direction orthogonal to the main scanning direction by 5, and the control circuit 12 controls the light emission of the light source and the light-receiving element in synchronization with the sub-scanning position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner for reading a bar code, and more particularly to a laser type scanner.

[0002]

2. Description of the Related Art Conventionally used laser scanners for reading barcodes scan one-dimensionally a barcode printed in two dimensions (vertical and horizontal) to perform reading.

Note that, as this type of apparatus, there are, for example, Japanese Patent Laid-Open Nos. 60-100273, 61-26185, and 3-25585.

[0004]

However, in the above-mentioned prior art, since the barcode is scanned one-dimensionally, there is uneven printing or stain called void or spot on the barcode. , A reading error occurred and I had to read it again. Therefore, there are problems in the reduction of the reading speed and the reliability of the reading result.

It is an object of the present invention to provide a bar code reading scanner which enables reliable reading even if the bar code label has uneven printing or dirt.

[0006]

To achieve the above object, the present invention irradiates a bar code label with a light beam from a light source and photoelectrically converts the reflected light by a light receiving element for decoding. In a scanner for reading a signal, the sub-scanning means for performing sub-scanning in a direction orthogonal to the main scanning direction by the light source, and the light emission control of the light source and the light-receiving element in synchronization with the sub-scanning position by the means. And a control means for controlling the above.

[0007]

According to the above-mentioned means, the light beam from the light source is sub-scanned in the direction orthogonal to the scanning direction to scan the bar code label in a sine wave shape. As a result, even if there is uneven printing or stains on the barcode label, the barcode label can be reliably read.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic operation of the present invention will be described before the description of the embodiments.

FIG. 2 shows a locus (thin line drawn diagonally) when the bar code is scanned using a conventional laser scanner.
Is. As described above, the spot diameter of the laser is made small in order to improve the resolution, and therefore, a linear locus is formed.

FIG. 3 shows a locus by the scanner of the present invention. The locus is a strip (or a plane) as compared with the conventional linear locus. FIG. 4 is an enlarged view of the locus of FIG. 3, and in actuality, sub-scanning is performed with simple vibration and modulation so as to be orthogonal to the scanning direction of the laser, not on the surface. , A sinusoidal trajectory is left.

Further, FIG. 5 shows a state in which a barcode having a void or a spot is scanned by a conventional scanner, and an output signal waveform obtained by converting the barcode into an electric signal. As shown in the figure, spots 2 and voids 3 are scattered on a scanning locus 4 formed in a direction orthogonal to the barcodes 1a and 1b. Normally, the output signal waveform of the scanner is "1" because the bar codes 1a and 1b are black, so the signal level is "0", and the spaces between the codes are white. However, if there are spots 2 and voids 3, the spot 2 portion becomes "1", the void 3 portion becomes "0", and there are two codes within the width of the barcode 1a. It is misread that one code is inserted between the codes 1b.

However, according to the present invention, as shown in FIG. 4, since the scanning locus draws a sine curve, there are N points (for example, 5 points) per modulation cycle during the scanning.
Sampling of (point) makes it possible to determine whether the area being scanned is white or black by using majority logic. As a result, the adverse effects of the spot 2 and the void 3 can be eliminated.

However, as shown in FIG. 6, in the scanning along the line of the bar code, the reading is performed without any problems as described above. However, as shown in FIG. , The sample point moves back and forth in the change area of the code, and the normal majority operation cannot be expected with a simple majority logic. Therefore, as shown in FIG. 8, it can be considered that the same number of scans as the number of samples (here, 5 points) in one modulation period are performed at the same time, although there is a substantial slight time lag. This is shown in FIG.
The output of black and white discrimination at the sampling point "5" means that there is only a time lag and the shape of the output waveform itself is the same. Therefore, the oblique scanning shown in FIG. 7 becomes equivalent to that in FIG. 6 by taking some synchronization.

Examples of the present invention will be described below.

FIG. 1 is a block diagram showing an embodiment of a bar code reading scanner according to the present invention.

Laser diode (LD) as a light source
Reference numeral 5 generates a laser beam toward the barcode label, the reflected light from the surface of the barcode label is received by the photodiode (PD) 6, and an electric signal corresponding to the reflected brightness is output from the photodiode 6. It An amplifier (AMP) 7 is connected to the photodiode 6, and sample-and-hold circuits (hereinafter referred to as S / H circuits) circuits 8a to 8c are connected in parallel to the amplifier 7 (in the above description, sampling is performed). Although it is assumed that the number of S / H circuits is 5, the number of S / H circuits is 3 here. S / H circuit 8a,
8s and 8c are connected to A / D (analog / digital) conversion circuits 9a, 9b and 9c, respectively, to which a synchronous circuit 10 is connected, and further to the synchronous circuit 10, a majority circuit 11 is connected. The output of the majority circuit 11 is sent to a decoder (not shown). Further, a control circuit 12 is provided to control the laser diode 5 and the S / H circuits 8a, 8s, 8c. This control circuit 12
Further, a sub-scanning driving unit 13 is connected to the sub-scanning unit 13 to drive the laser diode 5 for sub-scanning.

FIG. 9 is a block diagram showing an example of the scanning optical system, and FIG. 10 is a block diagram showing another example of the scanning optical system.
Here, in FIG. 9, a polygon mirror is used for the scanning mechanism, and in FIG. 10, a galvano mirror is used.

In the configuration of FIG. 9, the optical lens 14 and the polygon mirror 1 are provided on the emission optical path of the laser diode 5.
5 (here, they are drawn as circles for simplification of illustration, but actually form a polygon in the circumferential direction), the light reflected by the polygon mirror 15 is reflected by the bar code label 16. And scan from one side to the other as shown in FIG. The reflected light from this barcode label 16 is
The light is received by the photodiode 6, is input to the decoder 17 configured by a circuit excluding the laser diode 5 and the photodiode 6 in FIG. 1, and is subjected to decoding processing.

On the other hand, in the configuration of FIG. 10, a gas laser 18 is used in place of the laser diode 5, and a galvano mirror 19 is arranged on the emission optical path thereof. Since other configurations are the same as those in FIG. 9, redundant description will be omitted here.

In FIG. 9 and FIG. 10, the laser light from the light source (laser diode 5 or gas laser 18) is polygon mirror 15 or galvano mirror 19
The bar code label 16 is scanned by. The scanning locus at this time becomes linear, and it is necessary to perform the sub-scanning in a sine wave shape as shown in FIG. 6, but specifically, a direction perpendicular to the rotation direction of the polygon mirror (galvano In the case of a mirror, the laser light is shaken in the direction perpendicular to the vibration direction. As this means, it is possible to directly move the polygon mirror 15 and the galvano mirror 19, but other methods such as a method of vibrating the light source, a method of inserting a mirror in the middle of the optical path and vibrating this mirror are conceivable. . In addition, in this embodiment, in FIG.
As shown in FIG. 1, sub-scanning is performed by directly vibrating the light source.

In FIG. 11, the laser diode 5
And the shaft 22 is set near the laser diode 5 of the bar 20 having the permanent magnet 21 attached to the other end thereof.
1, an electromagnet 23 is disposed so as to face the laser diode 1, and an AC power supply 24 is applied to the electromagnet 23 to vibrate the laser diode 5 in the vertical direction in the drawing.

Next, the operation of the embodiment having the above configuration will be described.

A sine wave signal for driving (about 100 KHz at 100 scans / second) is applied from the control circuit 12 to the electromagnet 23 of the sub-scanning drive unit 13. As a result, FIG.
The scanning locus as shown in is obtained. In this case, a signal that controls the delay time from the current applied to the electromagnet 23 of the sub-scanning drive unit 13 to the start of the operation of the drive unit is controlled so that the sun ring is performed at each of 1 to 3 points. Circuit 12
To the S / H circuits 8a, 8s, 8c. Also, S
In order to ensure the operation of the / H circuits 8a, 8s, 8c, a signal as shown in FIG. 13 is also sent to the laser diode 5 so that it is turned on only during the sampling period.

As is apparent from FIG. 8, when the barcode is obliquely scanned, the output signals of the S / H circuits 8a, 8s and 8c are A / D converted by the A / D conversion circuits 9a, 9b and 9c. The correct information cannot be obtained by using them in order. Therefore, the synchronization circuit 10 is provided to achieve synchronization as shown in FIG. This figure shows a state in which the laser scanning light reaches the bar code part, and 1 to 3 are A at each sample point.
The / D conversion output is shown. Even though the sample point "1" is already on the barcode, the points "2" and "3" that are scanned with a time delay are not yet applied to the barcode portion. Therefore, from the buffer that stores several cycles of sub-scanning to the point where it is apparently first inverted to black (where sample point “1” is inverted in FIG. 14), the other sample points are combined to obtain sample point “1”. "-" 3 "
Is equivalent to the information on the point orthogonal to the scanning direction on the barcode. After synchronizing in this way,
In the present embodiment, after the inversion, by using a majority logic after one sampling period, it is possible to remove disturbances such as voids and spots.

FIG. 15 is a block diagram showing an example of a majority logic circuit.

The synchronization circuit 10 includes a binary conversion circuit 111.
Is connected to the output terminal of the binary conversion circuit 111, and one input terminal of a two-input comparator 112 is connected to the output terminal of a reference value generation circuit 113 that outputs a reference value to the other input terminal of the comparator 112. Are connected. For the comparator 112, for example, TTL “74LS85” can be used. This "74L
S85 "has two sets of A and B inputs each consisting of 4 bits.

For example, in the configuration of FIG. 1, the number of samples is three.
Therefore, the A input of the comparator 112 is A /
The outputs of the D conversion circuits 9a, 9b and 9c are passed through the synchronization circuit 10 and then converted into binary (converted into binary code) and connected. If white is "1" and black is "0", "0" is given for all black, "1" for white "1" black "2", and "1" for white "2" black "1". 2 ", if all white, it becomes" 3 ",
If the reference value “1” is given from the reference value generation circuit 113 to the B input of the comparator 112, it is determined that the A> B output has many whites. Using this output, many of the A inputs are known and as a result noise can be eliminated. Further, as shown in this embodiment, the S / H circuit 8
By using a, 8s, and 8c, it is possible to easily design the A / D conversion circuit, which is one of the bottleneck of speeding up.

[0028]

As described above, according to the present invention, the bar code label is irradiated with the light beam from the light source, and the reflected light is photoelectrically converted by the light receiving element to obtain a decoding signal. In the scanner, sub-scanning means for performing sub-scanning in a direction orthogonal to the main scanning direction by the light source, and control means for controlling light emission of the light source and control of the light receiving element in synchronization with the sub-scanning position by the means. Since the bar code label is provided, it can be reliably read even if the bar code label has printing irregularities or stains.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a barcode reading scanner of the present invention.

FIG. 2 is an explanatory diagram showing a locus when scanning is performed using a conventional laser scanner.

FIG. 3 is an explanatory diagram showing a locus by the scanner of the present invention.

FIG. 4 is an explanatory diagram showing the locus of FIG. 3 in an enlarged manner.

FIG. 5 is an explanatory diagram showing a scanning condition by a conventional scanner on a bar code having a void or a spot, and an output signal waveform at that time.

FIG. 6 is an explanatory diagram for explaining a problem when sub-scanning is performed on scanning light according to the present invention.

FIG. 7 is an explanatory diagram showing oblique scanning of scanning light according to the present invention.

FIG. 8 is an explanatory diagram showing a scanning light synchronization method according to the present invention.

FIG. 9 is a configuration diagram showing an example of a scanning optical system according to the present invention.

FIG. 10 is a configuration diagram showing another example of the scanning optical system.

FIG. 11 is a configuration diagram showing an example of a mechanism for performing sub-scanning.

FIG. 12 is an explanatory diagram showing a scanning locus according to the present invention.

FIG. 13 is a waveform diagram showing signal waveforms output from the control circuit to the laser diode and the sub-scanning drive unit.

14 is a waveform diagram showing an example of synchronization by the synchronization circuit of FIG.

FIG. 15 is a block diagram showing an example of a majority logic circuit.

[Explanation of symbols]

 5 Laser diode 6 Photodiode 7 Amplifier 8a, 8s, 8c S / H circuit 9a, 9b, 9c A / D conversion circuit 10 Synchronous circuit 11 Majority decision circuit 12 Control circuit 13 Sub-scanning drive unit 15 Polygon mirror 16 Bar code label 18 Gas laser 19 Galvano mirror 111 Binary conversion circuit 112 Comparator 113 Reference value generation circuit

Claims (1)

[Claims] 1. A bar code reading scanner for irradiating a bar code label with a light beam from a light source, and photoelectrically converting the reflected light by a light receiving element to obtain a decoding signal. And a control means for controlling the light emission of the light source and the light receiving element in synchronization with the sub-scanning position by the means. Scanner for reading.