JP2867779B2 - 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 reciprocating scanning mirror which scans light reciprocally and binarizes an electric signal corresponding to reflected light reflected from an object to be read on which a bar code is written. The present invention relates to a bar code reader that reads bar code data based on a count value obtained by counting a digitized signal at a predetermined sampling interval.

[0002]

2. Description of the Related Art Conventionally, a light source for projecting light, scanning means for reciprocatingly scanning light from the light source by a reciprocating scanning mirror, and an object to be read on which a bar code is written by scanning of light by the scanning means. Light receiving means for receiving the reflected light reflected from the light source and generating an electric signal corresponding to the amount of the received light; binarizing means for binarizing the electric signal from the light receiving means; 2. Description of the Related Art There is known a barcode reading apparatus including a counting unit that counts at a predetermined sampling interval, and a reading unit that reads barcode data based on a count value from the counting unit.

[0003]

However, since the scanning mirror reciprocates, acceleration occurs before and after the reversal of the reciprocating motion, and the plane scanning speed is not constant. On the other hand,
The frequency of the sampling clock used to determine the sampling interval when counting the binarized signal is constant. For example, as shown in FIG. 6, even when bar codes having the same module width are scanned, the pulse width of the binarized signal is not constant if the scanning mirrors have different plane scanning speeds.

For this reason, when counting is performed using a sampling clock having a constant period, in the case shown in FIG. 6, the count values are 6, 4, 3, 4, and 6 in sequence in spite of scanning bar codes having the same module width. It does not become constant. Therefore, for example, there is a possibility that a narrow bar is determined to be a wide bar even though it is a narrow bar. Therefore, it is necessary to perform software processing such as calculating the degree of dispersion and average value of the count values and correcting each count value based on the calculated values, and to calculate the average value or the like, a certain amount of data is required. Correction cannot be performed until the data is captured, and responsiveness deteriorates.

The present invention has been made in view of such a problem, and regardless of the difference in the plane scanning speed of the scanning mirror,
It is an object of the present invention to provide a bar code reader that can read bar code data correctly by a reading unit.

[0006]

In order to achieve the above object, a bar code reader according to the present invention has a light source for projecting light and reciprocating light from the light source. Scanning means for reciprocating scanning by a scanning mirror, and receiving light reflected from a reading target on which a barcode is written by scanning of light by the scanning means, and generating an electric signal corresponding to the amount of received light Means, binarizing means for binarizing an electric signal from the light receiving means, counting means for counting the binarized signal at a predetermined sampling interval, and the bar based on the count value from the counting means. A barcode reader having a reading means for reading code data, wherein the sampling clock is synchronized with the reciprocating motion of the scanning mirror and has a frequency which is an integral multiple of the reciprocating motion. A clock generating means for generating, said counting means at a sampling interval based on the sampling clock generated from the clock generating means, characterized by counting the binarized signal.

According to a second aspect of the present invention, there is provided a bar code reader, comprising: a light source for projecting light; scanning means for reciprocally scanning light from the light source by a reciprocating scanning mirror; and light scanning by the scanning means. Light receiving means for receiving reflected light reflected from a reading target on which a barcode is written and generating an electric signal corresponding to the received light amount, and binarizing means for binarizing the electric signal from the light receiving means And a reading means for reading bar code data based on the count value from the counting means, and counting means for counting the binarized signal at a predetermined sampling interval. A multiplication coefficient generating means for generating a multiplication coefficient proportional to the signal level of the scanning mirror control signal based on the scanning mirror control signal for controlling the reciprocation; Count value correcting means for multiplying the count value of the binary signal counted at the ring interval by the multiplication coefficient to correct the value, wherein the reading means reads the bar code data based on the corrected count value. Is read.

[0008]

According to the first aspect of the present invention, the scanning means scans the light from the light source by the reciprocating scanning mirror. The light receiving means receives the reflected light reflected from the reading target on which the bar code is written by scanning the light with the scanning means, and generates an electric signal corresponding to the received light amount. Is binarized.

On the other hand, the clock generating means generates a sampling clock synchronized with the reciprocating movement of the scanning mirror and having a frequency which is an integral multiple of the reciprocating movement. Then, the counting means converts the binarized signal output from the binarizing means to
The counting is performed at a sampling interval based on the sampling clock generated from the clock generating unit, and the reading unit reads the barcode data based on the count value.

As described above, since the binarized signal is counted at the sampling interval based on the sampling clock having a frequency which is an integral multiple of the reciprocating motion in synchronization with the reciprocating motion of the scanning mirror, the count value of the scanning mirror is Regardless of the difference in the plane scanning speed, the value becomes an appropriate value corresponding to the bar code, and the bar code data can be read correctly by the reading means.

Further, according to the bar code reader of the present invention, the multiplication coefficient generating means is proportional to the signal level of the scanning mirror control signal based on the scanning mirror control signal for controlling the reciprocating movement of the scanning mirror. The multiplication coefficient generated by the multiplication coefficient generated by the multiplication coefficient generation means is corrected by the count value correction means by multiplying the count value of the binary signal counted by the counting means at a fixed sampling interval. Then, the reading means reads the barcode data based on the corrected count value.

The generated multiplication coefficient is proportional to the scanning speed of the scanning mirror, and the count value of the binarized signal counted at a constant sampling interval by the counting means is inversely proportional to the scanning speed of the scanning mirror. Therefore, the corrected count value becomes an appropriate value corresponding to the bar code regardless of the difference in the plane scanning speed of the scanning mirror, and the bar code data can be correctly read by the reading means.

[0013]

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

As shown in FIG. 1, the optical system of the bar code reader according to the present embodiment includes a laser light source 2 for generating a laser beam,
A collimating lens 4 for converting the laser beam from the laser light source 2 into a parallel light beam;
A scanning mirror 8 that scans a laser beam transmitted through the bar code B to irradiate a bar code label 6 on which a bar code B is printed,
A photodetector 10 as a light receiving means for generating an electric signal corresponding to the amount of incident light, and a condenser lens 12 for condensing the laser light (scattered light) reflected from the barcode label 6 on the photodetector 10 It is configured.

The laser light source 2 is composed of a light emitting element such as a laser diode, a He-Ne laser, a focusing lens formed of a plano-convex lens, and an aperture stop. Project. The light detector 10 includes a light receiving element including a photodiode, a phototransistor, and the like, and an optical filter that transmits only light having the same wavelength as the laser light generated by the laser light source 2.

Next, the signal processing system of the bar code reader according to the present embodiment includes amplifying means 31 for amplifying a weak electric signal output from the photodetector 10, a binarizing means 33, a counting means 35, and an ECU. And a decoding unit 37 realized as one process. The drive system includes a mirror drive unit 41 for driving the step motor 5, a laser drive unit 43 for driving the laser light source 2, and the like. The control system emits laser light from the laser light source 2 via the laser drive unit 43. By driving the stepping motor 5 via the mirror driving means 41, the scanning mirror 8 is reciprocatedly rotated at a predetermined cycle, and the decoding unit 37 is synchronized with the rotation.
Is operated by the control unit 39. In general, the decoding unit 37 and the control unit 39 include a CPU, an RO,
The processing is realized as one process of an electronic control unit (ECU) including a microcomputer mainly including an M, a RAM, and the like.

The above-mentioned mirror driving means 41 is driven and controlled based on a mirror control frequency fx generated by a clock generating means 50 having a reference OSC 51 and a PLL circuit 53, and the counting means 35 is controlled by the clock generating means 50. Sampling clock to be made (frequency fos
It is configured to count at the sampling interval based on c). The mirror driving means 41 controls the oscillation cycle of the step motor 5 by changing the frequency of the mirror control frequency fx, or converts the frequency change into a voltage change (FV conversion).

The clock generator 50 will be described in more detail with reference to FIG. The PLL circuit 53 can be considered as a circuit for multiplying the reference frequency fs by N.
An integrator 56 using a low-pass filter (LPF) or the like, a voltage controlled oscillator (hereinafter, referred to as VCO) 58, and a 1 / N frequency divider (hereinafter, simply referred to as a frequency divider) 60 are basic constituent elements, and a loop is formed. The phase comparator 54 connected like a phase detector is a phase detection circuit, and a pulse output proportional to the phase difference is obtained. The pulse output is integrated by an integrator 56 to control the control terminal of the VCO 58. The VCO 58 changes the oscillation frequency according to the control voltage, and divides the oscillation frequency into N times by the frequency divider 60.
One input of the phase comparator 54. The reference frequency fs from the reference OSC 51 is input to the phase comparator 54, and by changing the set value N of the frequency divider 60, the output frequency fosc according to the set number N within the oscillation range of the VCO 58 from the reference frequency fs Is obtained.

The operation is briefly described below.
The output frequency fosc (= fs × N) from O58 is multiplied by (1 / N) by the frequency divider 60 and input to the phase comparator 54 as the comparison signal fx. Then, the loop acts to eliminate or maintain the phase difference between the input reference frequency fs and the comparison frequency fx. In this manner, the output frequency fosc is obtained by multiplying the reference frequency fs by N.

The sampling clock of the frequency fosc output from the VCO 58 is input to the counting means 35.
The comparison frequency fx from the frequency divider 60 is input to the mirror driving unit 41 as a mirror control frequency fx. The mirror driving means 41 determines the oscillation cycle of the scanning mirror 8 based on the mirror control frequency fx and causes the scanning mirror 8 to reciprocate.

In the bar code reader of the first embodiment configured as described above, the laser beam from the laser light source 2 is projected on the scanning mirror 8 and the bar code label 6 is scanned at a high speed. The reflected light from the bar code label 6 is condensed by the condenser lens 12 and then is
Incident on. Then, the photodetector 10 generates an electric signal corresponding to the amount of incident light, and the electric signal is amplified by the amplifying unit 31 and input to the binarizing unit 33.

The output from the binarizing means 33 is counted by a counting means 35 at a sampling interval based on a sampling clock (frequency fosc) generated by a clock generating means 50. The mirror control frequency fx for determining the oscillation period of the scanning mirror 8 is fed back to the phase comparator 54 to eliminate the phase difference from the reference frequency fs. As a result, the output frequency fosc multiplies the reference frequency fs by N.

Therefore, as shown in FIG. 3, the clock generating means 50 generates a sampling clock synchronized with the reciprocating movement of the scanning mirror 8 and having a frequency N times the reciprocating movement. Then, the counting unit 35 counts the binarized signal output from the binarizing unit 33 at a sampling interval based on the sampling clock. Since the scanning mirror 8 reciprocates, acceleration occurs before and after the reversal of the reciprocating motion, and the plane scanning speed is not constant. Even when the bar code B having the same module width is scanned, the pulse width of the binarized signal is not constant if the scanning speed of the scanning mirror 8 is different.

However, in this embodiment, the frequency of the sampling clock (hereinafter referred to as clock frequency) f.
Since osc is N times the reference frequency fs and is synchronous with and proportional to the plane scanning speed of the scanning mirror 8, the clock frequency fosc is low when the scanning plane speed is low, and the clock frequency fosc increases when the scanning plane speed is high. Become. Therefore, even if the pulse width of the binarized signal is not constant by scanning the bar code B having the same module width,
When the pulse width is large, the clock frequency fosc decreases.

Conversely, when the pulse width is small, the clock frequency fosc increases. FIG. 3 shows the clock frequency f
Although the case where osc is set to one time of the reference frequency fs is shown, as can be seen from the figure, if counting is performed using this sampling clock, the count value becomes a plane for the scanning mirror 8 to reciprocate. Regardless of the difference in scanning speed, the barcode B has an appropriate value (all three in this case), so that the decoding unit 37 can read barcode data correctly.

Next, a second embodiment will be described with reference to FIG. The same components as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. Similarly to the first embodiment, the reference OSC 51 whose oscillation frequency is controlled by the control unit 39 generates a clock having the reference frequency fs for determining the oscillation cycle of the step motor 5. Mirror driving means 41
Converts the change in the frequency of the reference frequency fs into a change in voltage to generate a scanning mirror control signal, and controls the reciprocating movement of the scanning mirror 8.

This scanning mirror control signal is configured to be input to the count value correcting means 85 via the AD converting means 81 for converting an analog value into a digital value and the multiplication coefficient generating means 83. The AD conversion means 81 converts the data into data proportional to the signal level (frequency, voltage value) of the scanning mirror control signal, and based on the data, the multiplication coefficient generation means 83 uses the data in proportion to the signal level of the scanning mirror control signal, that is, A multiplication coefficient proportional to the plane scanning speed of the scanning mirror 8 is generated.

On the other hand, the bar code data binarized by the binarizing means 33 is counted by the counting means 35 using a sampling clock having a constant period, and is converted into a bar code data count value. This count value is shown in FIG.
As shown in the conventional example, the count value is inversely proportional to the plane scanning speed of the scanning mirror 8, and the count value increases as the scanning speed decreases, and decreases as the scanning speed increases. This count value is input to the count value correction means 85.

In the count value correcting means 85, the above-described count value is multiplied by the multiplication coefficient input from the multiplication coefficient generation means 83 to perform correction. The generated multiplication coefficient is proportional to the plane scanning speed of the scanning mirror 8, and the count value of the binarized signal counted at a constant sampling interval by the counting means 35 is inversely proportional to the plane scanning speed of the scanning mirror 8. Accordingly, the corrected count value becomes an appropriate value corresponding to the bar code B regardless of the difference in the plane scanning speed of the scanning mirror 8, and the bar code data can be read correctly by the decoding unit 37.

As described above, the present invention is not limited to such embodiments at all, and can be implemented in various modes without departing from the gist of the present invention.

[0031]

As described above, according to the bar code reader according to the first aspect, the bar code reader is synchronized with the reciprocating movement of the scanning mirror and has a sampling interval based on a sampling clock having a frequency that is an integral multiple of the reciprocating movement. Since the digitized signal is counted, the value becomes an appropriate value corresponding to the bar code irrespective of the difference in the plane scanning speed of the scanning mirror, and the bar code data can be read correctly by the reading means.

According to the bar code reader of the present invention, the generated multiplication coefficient is proportional to the plane scanning speed of the scanning mirror, and the binarized signal counted by the counting means at a constant sampling interval. Since the count value is inversely proportional to the plane scanning speed of the scanning mirror, the corrected count value becomes an appropriate value corresponding to the bar code regardless of the difference in the plane scanning speed of the scanning mirror, and the bar code data is correctly read by the reading means. This has the effect of being able to read.

[Brief description of the drawings]

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

FIG. 2 is a block diagram illustrating a PLL circuit and the like of a clock generation unit.

FIG. 3 is a timing chart showing a plane scanning speed of a scanning mirror, a sampling clock, a count value, and the like in the first embodiment.

FIG. 4 is a schematic configuration diagram illustrating an entire configuration of a barcode reading device according to a second embodiment.

FIG. 5 is a timing chart showing a planar scanning speed of a scanning mirror, a barcode data count value, a multiplication coefficient, a corrected count value, and the like in the second embodiment.

FIG. 6 is a timing chart showing a plane scanning speed of a scanning mirror, a sampling clock, a count value, and the like in a conventional example.

[Explanation of symbols]

2 laser light source 5 step motor 6
Bar code label, 8 scanning mirror, 10 photodetector, 35 counting means, 37 decoding section,
39: control unit 41: mirror driving means
50 clock generating means 53 PLL circuit 81
... AD conversion means, 83 ... multiplication coefficient generation means, 85 ... count value correction means

Claims (2)

(57) [Claims] 1. A light source for projecting light, scanning means for reciprocally scanning light from the light source by a reciprocating scanning mirror, and light reflected by a bar code written by a scanning mirror by the scanning means. Receiving means for receiving the reflected light and generating an electric signal in accordance with the amount of received light; binarizing means for binarizing the electric signal from the light receiving means; A bar code reading device comprising: a counting means for counting at intervals; and a reading means for reading the bar code data based on the count value from the counting means. Clock generating means for generating a sampling clock having a frequency of an integral multiple, wherein the counting means includes a sampling clock generated by the clock generating means. Sampling interval based on the click bar code reader, characterized in that counting the binarized signal. 2. A light source for projecting light, scanning means for reciprocally scanning light from the light source by a reciprocating scanning mirror, and light reflected by a bar code written from a reading target on which a barcode is written by scanning of light by the scanning means. Receiving means for receiving the reflected light and generating an electric signal in accordance with the amount of received light; binarizing means for binarizing the electric signal from the light receiving means; In a bar code reader having a counting means for counting at intervals, and a reading means for reading bar code data based on the count value from the counting means, a bar code reader is provided based on a scanning mirror control signal for controlling a reciprocating movement of the scanning mirror. Multiplication coefficient generation means for generating a multiplication coefficient proportional to the signal level of the scanning mirror control signal, and a binarization signal counted at a predetermined sampling interval. A bar code reading device comprising: count value correcting means for correcting the count value by multiplying the count value by the multiplication coefficient; wherein the reading means reads the bar code data based on the corrected count value. .