JPH05324880A - Bar code reader - Google Patents

Abstract

PURPOSE:To ensure the correct reading of bar codes over a wide range of distances, angles, etc., of the reading positions. CONSTITUTION:A peak detecting part is reset at the time t10 synchronously with the rising edge of a negative pulse CL10 of a synchronizing signal (a), latches and outputs the peak value 'P10' of a bar code amplifying signal (b) at the time t10-1, and latches and outputs the peak value 'P12' at the time t10-2. Then, the peak detecting part is reset again at the time t11 synchronously with the rising edge of a negative pulse CL11 of the next signal (a) when the value obtained by digitizing the larger peak value 'P12' is smaller than the lower limit value. At the same time, a gain switching part is switched by a gain switch deciding part and the gain is increased up to an optimum level. Therefore, the peak value 'P13' is recovered in a range of the proper value with the peak detection carried out at the time t11-1. Then, the signal (b) can be converted into the digital data that can be processed by a host computer.

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 used in a bar code system.

[0002]

2. Description of the Related Art Conventionally, for example, when a product is moved on a belt conveyor and automatically packed in a box, in order to calculate sales in real time, a product code indicating a product name or a selling price is transferred during the movement. There is a bar code system that automatically reads from the product. This barcode system is a barcode that is printed and displayed on tags or packaging based on data sources such as product names and sales prices, and a barcode that reads the barcode, converts it into a signal that can be processed by a computer, and outputs it. It consists of a code reader and an operator who operates them.

As the above-mentioned bar code, a multi-level code which represents a binary code processed by a computer by a combination of a bar (line) and a space (blank) is widely used.

Further, the bar code reader generally has a detecting section 7 for reading a bar code 72, as shown in FIG.
3, a decoding section 74 for decoding the bar code read by the detection section 73, and a display 75 for displaying the information decoded by the decoding section 74 are integrally incorporated in one housing 71. ing.

An LED, a detector (detector), a comparator and the like are provided inside the detecting section 73, and light from the LED, which is a light source, is applied to a bar code and the reflected light is collected by an optical lens. Light is emitted and its intensity (black and white of barcode) is converted into a pulse train of electric signals. The decoding unit 74 is provided with a decoder and the like, and converts the signal of the pulse train output from the detection unit 73 into a signal that can be easily processed by a computer and outputs it to the host computer or records it in an internal memory. The displayed product name is displayed on the display 75.
The price etc. are displayed.

[0006] Then, the operator can detect the distance between the bar code reader and the bar code that can read the bar code optimally,
The position of the barcode with respect to the barcode reader such as the angle is confirmed in advance, and the reading work is executed while setting the barcode attached to the product to the position where it can be optimally read.

[0007]

However, even if the bar code is set at the position where the bar code can be read optimally, the bar code becomes dirty and PCS (Print Contrast Signal: There was a problem that reading errors often occurred due to a decrease in black and white brightness of printed barcodes and variations in reading depth (distance range between barcode reader and barcode that can be optimally read). .. Further, if the conditions of the position such as distance and angle are narrowed to prevent reading mistakes, there is a problem that the degree of freedom of the barcode setting work is reduced and the work efficiency is reduced accordingly.

The above reading error occurs because the pulse waveform reflected from the bar code is attenuated, or the reflected light becomes excessive and the amplifier is saturated, resulting in unclear pulses and correct pulse width and pulse interval. It is considered that this occurs because width information cannot be obtained.

The object of the present invention is to switch the amplification gain of reflected light from a bar code to the optimum gain so that the gain is high in the case of attenuation and low in the case of excess, for example, dirt, tags, packaging, etc. This is to enable correct reading of a barcode over a wide range such as the distance and angle of the reading position regardless of the state of the barcode on the printed surface having different reflectance.

[0010]

The present invention is applied to a bar code reader for reading bar code information by converting reflected light obtained by optically scanning a bar code into an electric signal.

The means of the invention described in claim 1 is as follows (see the block diagram 1 of the present invention in FIG. 1). An amplifying means 1 for amplifying an analog electric signal converted from reflected light obtained by optically scanning the bar code, and a detecting means 2 for detecting a peak value of the analog electric signal amplified by the amplifying means 1. , Conversion means 3 for digitizing the peak value of the analog electric signal detected by the detection means 2
And switching means 4 for switching the amplification gain of the electric signal so that the electric signal is amplified to the optimum amplitude by the amplification means 1 on the basis of the peak value digitized by the conversion means 3, and switched by the switching means 4. Level conversion means 5 for converting the analog electric signal amplified by the amplification means 1 into binary levels of “H” level and “L” level based on the gain, and of the binary level converted by the level conversion means 5. The decoding output means 6 decodes the signal and outputs the decoding result. Means of the invention described in claim 2 is as follows (see the block diagram (part 2) of the invention of FIG. 2).

Amplifying means 1 for amplifying the analog electric signal converted from the reflected light obtained by optically scanning the bar code, and detection for detecting the peak value of the analog electric signal amplified by the amplifying means 1. Based on the means 2, the conversion means 3 for digitizing the peak value of the analog electric signal detected by the detection means 2, and the peak value digitized by the conversion means 3, the electric signal is optimized by the amplification means 1. An informing means 7 for informing the optimum amplification gain of the electric signal so as to be amplified to the amplitude, and an arbitrarily operable input means 8 for switching the amplification gain of the electric signal to the optimum gain based on the notification by the informing means 7. And a level conversion means 5 for converting the analog electric signal amplified by the amplification means 1 into a binary level of "H" level and "L" level.
And a decoding output means 6 for decoding the binary level signal converted by the level conversion means 5 and outputting the decoding result.

[0013]

The operation of the means of the present invention is as follows. In the invention according to claim 1, the analog electric signal converted from the reflected light obtained by optically scanning the barcode is amplified by the amplifying means 1. The peak value of the amplified analog electric signal is detected by the detecting means 2, and the detected peak value is converted into a digital value by the converting means 3. Then, based on the converted digital value, the amplification gain of the electric signal is switched by the switching unit 4 so that the amplification unit 1 amplifies the electric signal to the optimum amplitude. Based on the gain thus switched, the analog electric signal amplified by the amplification means 1 is converted into serial digital data by the data conversion means 5, and the converted serial digital data is decoded by the decoding output means 6 and The decryption result is output.

In the second aspect of the invention, the amplifying means 1 amplifies the analog electric signal converted from the reflected light obtained by optically scanning the bar code. The peak value of the amplified analog electric signal is detected by the detecting means 2, and the detected peak value is converted into a digital value by the converting means 3. Then, the notifying means 7 notifies the optimum gain of the electric signal so that the amplifying means 1 amplifies the electric signal to the optimum amplitude based on the converted digital value. Based on this notification, the amplified electric signal is switched to the optimum gain by the input means 8 which can be operated arbitrarily. Based on the gain thus switched, the analog electric signal amplified by the amplification means 1 is converted into serial digital data by the data conversion means 5, and the converted serial digital data is decoded by the decoding output means 6 and The decryption result is output.

Therefore, the reflected light amplification gain of the bar code can be switched to the optimum gain so as to obtain a high gain in the case of attenuation and a low gain in the case of excess, for example, dirt or a different reflectance such as tags or packaging. It becomes possible to correctly read the barcode over a wide range such as the distance and angle of the reading position regardless of the state of the barcode on the printing surface.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 3 is a diagram illustrating the internal configuration of the barcode reader according to the embodiment.

In the figure, the bar code reader 20 has a detection section 23, a decoding section 24 and a gain control section 25. The detection unit 23 includes an LED 23-1, which serves as a light source, a reflector 23-2 which reflects the light of the light source while rotating and irradiates the bar code at a predetermined scanning angle, and detects the irradiation light reflected from the bar code. 23-3, which is a photosensor for converting into an analog electric signal by means of an optical sensor, a preamplifier 23-4 for first amplifying a signal input from the photodiode 23-3, and a gain described in detail below with respect to the outputs of the preamplifier 23-4 A switching amplifier 23-6 that amplifies while switching between four resistors, and four resistors each having a different resistance value,
A gain switching unit 23-7 composed of four switches respectively connected in series to those resistors, the switching amplifier 23-
6, the comparator 23-8 which binarizes the signal amplified by 6 into "H" level and "L" level, and the reflector 23-
There is provided a sync signal output unit 23-9 which detects the irradiation light from 2 at a predetermined position and outputs the detection signal as a sync signal a to a gain switching determination unit 25-3 of the gain control circuit 25 described later.

The decoding unit 24 includes a serial / parallel conversion unit 24-1, a memory unit 24-2 including a RAM (Random Access Memory), and a CPU (Central Processing).
A barcode decoding unit 24-3 including a unit) is provided. Further, although not particularly shown, a ROM, an MPU having a built-in clock oscillation circuit, and a power supply for operating the detection unit 23, the decoding unit 24, and the gain control unit 25 are provided.

The serial / parallel converter 24-1
Is the bar / value depending on the logic value (“H” or “L”) of the binarized serial signal (pulse signal of indefinite width) input from the comparator 23-8 of the detection unit 23.
The pulse width and the pulse interval are measured by the reference clock while discriminating the space, and a bit image consisting of "1" and "0" is generated based on the measured width information and the discriminated bar / space. , The bit image is converted into a parallel signal having a predetermined bit width, for example, 16 bit width. The memory unit 24-2 temporarily stores the parallel signal. In addition, the bar code decoding unit 24-
3 reads out the parallel signal from the memory unit 24-2, analyzes and encodes the parallel signal, and outputs the parallel signal to the host computer via an interface electronic circuit or the like (not shown). further,
If the number of binarized pulses is equal to or less than a predetermined number, the barcode decoding unit 24-3 determines that there is no label (barcode tag or barcode printed on the package), and the determination result And outputs the label present / absent signal d to the gain switching determination unit 25-3 of the gain control unit 25.

The gain control section 25 includes a peak detection section 25-1 for detecting the peak value of the analog signal input from the switching amplifier 23-6 of the detection section 23, and an A / A for digitizing the detected peak value. The D conversion unit 25-2 and the gain switching unit 23 based on the digitized peak value.
While switching the switch of -7, the label presence / absence signal d input from the barcode decoding unit 24-3 of the decoding unit 24 or the synchronization signal a input from the synchronization signal output unit 23-9 of the detection unit 23. A gain switching determination section 25-3 is provided for outputting a reset signal e based on the above and resetting the peak detection section 25-1.

The relationship between the bar code amplified signal b output from the switching amplifier 23-6 and the output of the peak detection section 25-1 for detecting its peak value will be described with reference to the time chart of FIG. From the top of the figure, the synchronization signal a (see the figure
(a)), a bar code amplified signal b (FIG. 2 (b), and an output c of the peak detector (FIG. 2 (c)).

The synchronizing signal a has a constant period, for example, 5 msec.
Negative pulse CL0, CL1, CL2 every (millisecond) ...
·have. The bar code amplified signal b has the same value 1 by the above-mentioned light source irradiation and reflected light detection performed every period T0, T1, T2, ...
Each bar code is repeatedly read and the switching amplifier 23
An analog waveform signal is output from -6.

As described above, the amplified bar code signal b is binarized by the comparator 23-8 and input to the decoding section 24. In the decoding unit 24, at least two consecutive periods, for example, T0 and T1, or T1 and T.
If the bar code signals in 2 and the like are the same, it is determined that the bar code has been correctly read.

The peak detector 25-1 is reset at time t0 in synchronization with the rising edge of the negative pulse of the synchronizing signal a, and at time t0-1, the peak value "P1" of the bar code amplified signal b. , And output
Latching and outputting the peak value "P2" at time t0-2 is repeated for each of the above periods T0, T1, T2, ....

The peak values "P1", "P2" ...
Are digitized by the A / D converter 25-2. In this digitization, the output of the switching amplifier 23-6 is divided into 16 steps from 0 to the saturation point Px, for example, "0" to "15", and digitized according to this division. Then, for example, if the value is “3” or less, the amplification gain (gain) is low and inappropriate, and if the value is “13” or more, the gain is too high and this is also inappropriate, “4” to “12”. If so, it is determined that the gain is optimum.

The time chart of FIG. 5 shows an example in which, when the peak value c of the bar code amplified signal b is inappropriate because the gain is low, the inappropriate gain can be appropriately switched. .. Also in the same figure, from the top, the synchronizing signal a (the same figure (a)), the bar code amplification signal b (the same figure (b), and the output c of the peak detection section (the same figure (c)).

Also in this case, the peak detector 25-1
It is reset at time t10 in synchronization with the rising edge of the negative pulse CL10 of the synchronizing signal a, and at time t10-1, the peak value "P10" of the barcode amplified signal b is latched and output, and at time t10-2. Then, the peak value "P12" is latched and output. Since the digitized value of the higher peak value "P12" is smaller than the predetermined lower limit value, for example "2", the negative pulse C of the next synchronizing signal a
The peak detection unit 25-1 is reset at time t11 in synchronization with the rising edge of L11, and at the same time, the gain switching determination unit 25-3 switches the gain switching unit 23-7 to optimize the gain. Be pulled up. Therefore, the subsequent detection at time t11-1 indicates that the peak value "P13" has recovered to an appropriate value range. Although not shown in particular, when the digitized peak value exceeds the upper limit value, for example, "14" or the like, the switch is switched so that the gain is optimally lowered.

When the gain is lowered, for example, when the gain is lowered, all the four switches are turned on, and the input and output of the switching amplifier 23-6 are connected in parallel. Short circuit through a resistor. on the other hand,
To increase the gain, for example, all four switches are turned off so that the output of the preamplifier 23-4 is directly input to the switching amplifier 23-6 via the resistor connected in series in the middle. There are 16 types of these gains that change due to the switch operation, depending on the combinations when four resistors having different resistance values are selected, and the selection of the combinations is performed by a switch selector (not shown). Then, the switch selector is set on the basis of the digitized peak value, and the switch selector selects the optimum gain from these 16 ways.

Next, the operation of the gain switching determination process of the first embodiment configured as described above will be described with reference to the flowchart of FIG. Note that this processing is performed by the gain switching determination unit 25-3 of the gain control unit 25 shown in FIG.

In the flowchart of FIG. 6, first, it is determined whether or not the synchronization signal a is turned on (S6).
1). Thereby, it is determined whether or not the LED 23-1 of the light source is turned on.

If it is on, it is determined that the system is operating, the analog / digital conversion by the A / D converter 25-2 is started, and the conversion result is input (S62). Thereby, for example, the peak values P1 and P2 of the barcode amplified signal b as shown in FIG.
Etc. corresponding to the digital data are obtained.

Then, it is judged whether or not the signal input from the bar code decoding section 24-3 has "label" (S63). If the signal has "label", the above analog / digital signal is obtained. The optimum gain value is determined based on the digital data obtained by the conversion (S64).
This determination is made, for example, by preparing in advance a table in which the number of stages of gain value selection among 16 stages to be raised (or lowered) corresponding to the digital values of "0" to "15" is prepared and This is performed by obtaining a range (stage) to be changed, and determining a new switch selection position from the current switch selection position of the gain switching unit 23-7 based on the obtained range.

Next, the peak detector 25-1 is reset (S65). As a result, until the next synchronization,
Detection of a new peak value is restarted from the lowest value "0" (see FIG. 5 (c)).

Then, the switch selector is set based on the switch selection position determined in S64, and the switch selector output is turned on (S66). As a result, the switch of the gain switching unit 23-7 is switched,
The optimum gain can be obtained (see Fig. 5 (b)).

If the label is not present in step S63, the process immediately proceeds to step S65. If the synchronizing signal a is not turned on in step S61, the process waits until it is turned on.

In the above embodiment, the gain is automatically switched based on the detected peak value, but the automatic gain is not switched in this way, and the optimum gain is calculated and displayed based on the detected peak value. However, the gain switching may be manually input according to this display. this,
A second embodiment will be described below.

FIG. 7 is a block diagram of the bar code reader of the second embodiment. Components having the same functions as those in the first embodiment are designated by the same reference numerals. In the figure, the bar code reader 20 'has a detection unit 23, a decoding unit 24, and a gain control unit 25'. The detection unit 23 and the decoding unit 24 have the same configurations as in the first embodiment. On the other hand, in the gain control unit 25 ', the gain switching determination unit 25-3 of the gain control unit 25 of the first embodiment is removed, and instead, the gain announcement unit 25'-4 and the display 25'.
-5 and a gain changeover switch 25'-6 are provided, and the other peak detection section 25-1 and A / D conversion section 25-2 are the same as those in the first embodiment.

The gain announcer 25'-4 is A
The optimum gain is determined based on the digitized peak value input from the / D conversion unit 25-2, and the data of the optimum gain is output to the display unit 25'-5. Further, the synchronization signal a input from the synchronization signal output unit 23-9 or the “label present / input” from the barcode decoding unit 24-3.
Based on the "no" signal d, the reset signal e is output to the peak detector 25-1.

The display 25'-5 displays the optimum gain data input from the gain announcer 25'-4, such as the number of times the gain changeover switch 25'-6 should be operated, and the bar code decoder. The bar code decoding data input from 24-3 is displayed.

The gain changeover switch 25'-6 outputs a gain changeover signal to the gain changeover section 23-7 based on the switch operation of the operator. The switching amplifier 23-6
The relationship between the barcode amplified signal b output from the device and the output of the peak detection unit 25-1 that detects the peak value is as follows:
This is exactly the same as the case of the embodiment (see FIGS. 4 and 5).

Next, the bar code reader 2 having the above-mentioned configuration
The operation of the 0'gain switching notification process will be described with reference to the flowchart of FIG. It should be noted that this process is performed by the gain announcer 25'- of the gain controller 25 'shown in FIG.
4 is performed.

Further, in the flowchart of FIG. 8, steps S81, S82 and S83 are exactly the same as steps S61, S62 and S63 of the flowchart of the first embodiment.

In the processing of the second embodiment, if the signal input from the bar code decoding section 24-3 is "with label" in step S83,
The optimum gain value is determined based on the digital data obtained in step S82, and the determined gain value is output to the display 25'-5 (S84). As a result, how many steps the gain value is increased (or decreased) is displayed on the display 25'-5, and the operator operates the gain changeover switch 25'-6 while watching the display to switch the gain to the optimum value. be able to.

Following S84, the peak detector 25-1
Is reset (S85). As a result, detection of a new peak value is restarted from the lowest value "0" until the next synchronization (see FIG. 5 (c)).

If it is not "labeled" in step S83, the process immediately proceeds to step S85. In addition,
In the above-described first and second embodiments, the gain switching unit 23-7 is composed of four resistors and switches, respectively. However, without being limited to this, an arbitrary number of resistors and switches may be used. You may.

[0046]

As described above in detail, according to the present invention, the amplification gain of reflected light from a bar code can be switched to the optimum gain so that the gain is high in the case of attenuation and low in the case of excess. Therefore, it is possible to correctly read the barcode over a wide range such as the distance and angle of the reading position regardless of the dirt or the state of the barcode that is printed on the surface having different reflectance such as tags and packaging. Therefore, it is not necessary to narrow the bar code reading position conditions such as distance and angle in order to prevent reading errors, and the degree of freedom in bar code setting work is large, so it is possible to improve work efficiency accordingly. Become.

[Brief description of drawings]

FIG. 1 is a block diagram (1) of the present invention.

FIG. 2 is a block diagram (2) of the present invention.

FIG. 3 is a configuration diagram of a barcode reader according to the first embodiment.

FIG. 4 is a diagram illustrating a relationship between a barcode detection signal and a peak hold signal.

FIG. 5 is a diagram illustrating an example in which an inappropriate gain is appropriately switched.

FIG. 6 is a flowchart of a gain switching determination process according to the first embodiment.

FIG. 7 is a configuration diagram of a barcode reader according to a second embodiment.

FIG. 8 is a flowchart illustrating a gain switching notification process according to the second embodiment.

FIG. 9 is a diagram illustrating a conventional barcode reader.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 amplification means 2 detection means 3 conversion means 4 switching means 5 data conversion means 6 decoding output means 7 notification means 8 input means

Claims (2)

[Claims] 1. A bar code reader for reading bar code information by converting reflected light obtained by optically scanning a bar code into an electric signal, and a reflection obtained by optically scanning the bar code. Amplifying means for amplifying analog electric signal converted from light (1)
A detecting means (2) for detecting a peak value of the analog electric signal amplified by the amplifying means (1); and a converting means for digitizing the peak value of the analog electric signal detected by the detecting means (2). A switching means for switching the amplification gain of the electric signal so that the electric signal is amplified to an optimum amplitude by the amplification means (1) based on the peak value digitized by the conversion means (3). Means (4), and based on the gain switched by the switching means (4), converts the analog electric signal amplified by the amplification means (1) into a binary level of "H" level and "L" level. Level conversion means (5) and decoding output means (6) for decoding the binary level signal converted by the level conversion means (5) and outputting the decoding result.
And a bar code reader. 2. A bar code reader for reading bar code information by converting reflected light obtained by optically scanning a bar code into an electric signal, wherein a reflection obtained by optically scanning the bar code. Amplifying means for amplifying analog electric signal converted from light (1)
A detecting means (2) for detecting a peak value of the analog electric signal amplified by the amplifying means (1); and a converting means for digitizing the peak value of the analog electric signal detected by the detecting means (2). Means (3), and notifies the optimum amplification gain of the electric signal so that the electric signal is amplified to the optimum amplitude by the amplifying means (1) based on the peak value digitized by the converting means (3). An informing means (7), an arbitrarily operable input means (8) for switching the amplification gain of the electric signal to an optimum gain based on the informing by the informing means (7), and the amplifying means (1) Level conversion means (5) for converting the analog electric signal amplified by the two-level signals of "H" level and "L" level, and decoding of the binary level signal converted by the level conversion means (5) Decryption output hand that outputs the decryption result (6)
And a bar code reader.