JPH04268681A - Optical reader - Google Patents

Abstract

PURPOSE:To quickly detect the erroneous reading of a bar code generating an error in the number of digits (characters) of the bar code. CONSTITUTION:In a constant memory 253, the constant representing the number of bar codes is stored. A bit image BI is supplied to a character counter 2512 as well as the number of digits is counted. After the writing of the bit image BI in a stop code bit image memory 24 and a character code bit image memory 23, a digit number comparator 254 operates and the count value of the character counter 2521 and the constant of a constant memory 253 are compared. At the time of unmatch, the digit number comparator 254 outputs an error signal ERR4, and a character conversion reset signal CERT performing the next reading of the bar code is generated from an error processing circuit 29.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to an optical reading device for reading barcodes printed on media such as paper.
In particular, it relates to barcode reading error detection.

0002

[Prior Art] A barcode is a barcode in which characters such as letters and numbers are coded using multiple bars of different widths, so that a string of characters such as a product's price or product name can be represented by an array of bars. This is what I did. The code representing a character is hereinafter referred to as a character code, and the number of bars representing one character code, the thick bar,
The pattern of combinations of thin bars differs depending on the barcode format, but in all formats, a margin (blank space), a start code, and a stop code are displayed before and after a row of bars representing all character codes. There are bar rows.

[0003] In the following, for clarity of explanation, the format of the barcode is assumed to be Interleaved 2 of 5. This represents one character with five black bars,
Furthermore, five white bars at intervals between black bars represent one character. One barcode represents a plurality of character codes, each character code being one digit.

[0004] In this type of barcode display, the part of the background color of the medium of a predetermined width on the left side of the barcode display is used as a start margin, and the part of the background color of the medium of a predetermined width on the right side of the barcode display is used as a stop margin. These margins are used to determine whether a barcode is displayed. The thin bar at the left end of the barcode display and the thin bar following it represent a start code, and the thin bar at the right end and the thick bar one place to the left represent a stop code. Between these start and stop codes, there is a character code that determines the respective display contents by a combination of a predetermined number of thin bars or thick bars (black bars) and thin spaces or thick bases (white bars). is displayed. Here, assuming that the direction in which the character codes are arranged (that is, from the start code to the stop code) is the forward direction, barcodes are generally read in the above forward direction, but in the reverse direction. In such cases, the stop code is read as if it were a start code, and the start code is read as if it were a stop code. This makes it possible to determine the reading direction of the barcode.

An optical reading device for reading such a barcode is called a barcode scanner. Hereinafter, an example of a conventional barcode scanner using a line sensor will be explained with reference to FIGS. 2 and 3. However, in the figure, 1 is a reading signal latch circuit, 2 is an illumination unit, 3 is an optical imaging unit, 4 is a 1-scan counter, 5 is a media, 6 is a bar code, 7 is a start pulse generation circuit, and 8 is a start pulse generation circuit. A pulse width setting circuit, 9 a level detection circuit, 10 a photoelectric conversion section, 11 and 12 a frequency dividing circuit, 13 an oscillation circuit, 14 a binarization circuit, 15 a scanning number constant memory, 16 a scanning number counter, 17 is a scanning number comparator, 18 is an edge detection circuit, 19 is a timer counter, 20 is a count value memory, 21 is a count value memory control section, 22 is a bit image converter, 23 is a character code bit image memory, 24 is a A stop code bit image memory, 25 a bit image memory control section, 251 an address counter, 252 an address decoder, 2511 a bit counter, 2512 a character counter, 26 a start/stop determination section, 27 a character conversion section, 28 is a character code match comparator;
29 is an error processing circuit, 30 is a constant memory, 31 is a data matching number counter, 32 is a data matching number comparator, 3
3 is an output data conversion section.

In FIG. 2, an oscillation circuit 13 is always operating, and its output signal is divided by a frequency dividing circuit 11 to form a clock φ1, and by a frequency dividing circuit 12 to form a clock φ2. be done. The clock φ1 is supplied to a photoelectric conversion section 10 consisting of a line sensor and a one-scan counter 4, and the clock φ2 is supplied to a timer counter 19.

A read start signal S is received from a host device (not shown).
When the reading signal latch circuit 1 is supplied, the reading signal latch circuit 1 is set and outputs the reading signal READ, which is supplied to the illuminating section 2 and the start pulse generating circuit 7. The illumination unit 2 has an LED as a light emitting element, and lights up the LED in response to a reading signal READ to illuminate the printing area of the barcode 6 on the medium 5. The light reflected from this printing area is transmitted to the optical imaging section 3.
The barcode 6 is irradiated onto the light-receiving surface of the line sensor, which is the photoelectric conversion section 10, through the optical imaging section 3, and an image of the barcode 6 is formed on the light-receiving surface of the line sensor. The photoelectric conversion unit 10 will be described below as a line sensor.

The start pulse generating circuit 7 is operated under the following four conditions: (1) the scan end signal SED is supplied from the 1-scan counter 4; (2) the reading signal READ is supplied from the reading signal latch circuit 1;
(3) The pulse width setting circuit 8 has completed the pulse width setting and the set value has been sent. (4) The character conversion end signal CED has been supplied from the character conversion section 27. When all of these conditions are satisfied at the same time, a start pulse ST is generated. Such conditions are hereinafter referred to as pulse generation conditions.

In the initial state, the one-scan counter 4 receives the scan end signal SED, the pulse width setting circuit 8 receives the initial value set, and the character converter 27 (FIG. 3) receives the character conversion end signal CED. When the reading signal READ is started to be supplied from the reading signal latch circuit 1, the start pulse generation circuit 7 satisfies the pulse generation conditions and starts the pulse width determined by the initial value of the pulse width setting circuit 8. Generate pulse ST. This start pulse ST is supplied to the one-scan counter 4 and the line sensor 10.

The line sensor 10 receives a start pulse ST.
The image on the light receiving surface is changed by 1 every time clock φ1 is supplied.
The barcode 6 is scanned and read pixel by pixel. As a result, the line sensor 10 outputs electrical signals having different levels for the black bar and the white bar of the barcode 6. Furthermore, the one-scan counter 4 starts counting the clock φ1 in response to the start pulse ST, and receives the scan end signal S.
When ED is no longer output and the clock φ1 for one scan of the line sensor 10 is counted, the scan end signal SE is output again.
Output D. This scan end signal SED is supplied to the start pulse generation circuit 7, the scan number counter 16, the count value memory 20, and the count value memory control section 21.

The pulse width of the start pulse ST determines the charging time of each capacitor forming a pixel in the line sensor 10, and the line sensor 10
The magnitude of the output signal level is determined. This output signal is supplied to a level detection circuit 9 to detect the magnitude of the level, and in accordance with the detection result, a pulse width setting circuit 8 sets a pulse width that provides an optimum level. When the start pulse generation circuit 7 is supplied with the scan end signal SED again from the 1-scan counter 4 and satisfies the pulse generation conditions, it again generates a start pulse ST with a pulse width according to the setting value of the pulse width setting circuit 8. The line sensor 10 is started to scan, and the 1-scan counter 4 is started to count. In this way, the line sensor 10 repeatedly scans the barcode 6.

The output signal of the line sensor 10 is binarized in level by a binarization circuit 14 and then sent to an edge detection circuit 18.
Its rising and falling edges are detected. The edge pulse EG output from the edge detection circuit 18 is supplied to a timer counter 19 and a count value memory control section 21.

The timer counter 19 counts the clock φ2 from the frequency dividing circuit 12 using the edge pulse EG as a reset signal. Therefore, the timer counter 19 outputs a count value N representing the width of each bar of the bar code 6. This count value N is determined by the count value memory control section 2.
1 is written into the count value memory 20 controlled by 1. When all the count values N of the barcode 6 are written into the count value memory 20 and the one-scan counter 4 outputs the scan end signal SED, the count value memory 20 enters the read mode and is controlled by the count value memory controller 21. Then, the written count values N are read out from the count value memory 20 in the order in which they were written.

The count value N outputted from the count value memory 20 is supplied to a bit image converter 22, where it is compared with a preset threshold value and converted into a bit image BI representing the type of bar.

Next, FIG. 3 will be explained. The bit image BI from the bit image converter 22 is supplied to a character code bit image memory 23, a stop code bit image memory 24, and a bit image memory controller 25. Bit image memory control section 25
consists of an address counter 251 and an address decoder 252. The address counter 251 receives the bit image BI (i.e., the barcode 6 to be read (FIG. 2).
Bit counter 251 that counts the number of bars in )
1, and a character counter 2512 that counts by 1 each time this bit counter counts the bit image BI for one character after counting the bit image BI for the stop code at the front of the barcode 6.
It is made up of. Address decoder 252 decodes the count values of bit counter 2511 and character counter 2512 to form and output an address signal.

Here, the address signal outputted from the address decoder 252 consists of a decoded value of the count value from the bit counter 2511 and a decoded value of the count value from the character counter 2512, and the bit counter 2511 decodes the bit image of the stop code. During the period for counting BI, the count value of the character counter 2512 is 0. When the bit counter 2511 counts the first bit image BI for the first bar of the character code, the character counter 2512 counts by 1 and the count value becomes 1. From then on, the bit counter 2511 counts the bit image BI for one character. B
Each time I is counted, the count value of the character counter 2512 is incremented by one.

On the other hand, only the address specified by the address signal from the address decoder 252 is set in the stop code bit image memory 24 when the count value of the character counter 2512 is 0. Only the address specified by the address signal from the address decoder 252 when the count value of the character counter 2512 is other than 0 is set.

Therefore, by the operation of the bit image memory control section 25 and the address settings of the memories 23 and 24, the bit image BI of the stop code is written into the stop code bit image memory 24, and then the character code bit image BI is written. The character code is written into the bit image memory 23. In addition, In
In the case of terleaved 2 of 5, the bit image BI corresponding to the black bar and the bit image BI corresponding to the white bar are separated and written into the character code bit image memory 23.

After reading out the count value N from the count value memory 20 (FIG. 2), the character code bit image memory 23 and the stop code bit image memory 2 are read out.
When the bit image BI has been written in step 4, these memories 23 and 24 enter the read mode, and the bit image control memory 25 generates an address signal after the bit counter 2511 and character counter 2512 are cleared. start. With this address signal, first,
Data SCD consisting of a bit image of a stop code is read out from the stop code bit image memory 24 and supplied to the start/stop determination section 26, and then data SCD consisting of a bit image of a stop code is read out from the character code bit image memory 23 in a number equal to the number of bars for one character. The data CCD consisting of bit images are sequentially read out and supplied to the character converter 27. counter 251
1 counts the internal clock by a number equal to the number of bars of one character and generates an address signal, thereby reading out the next data CCD from the character code bit image memory 23.

In the start/stop determining section 26,
The bit pattern (hereinafter referred to as
A bit pattern (hereinafter referred to as a detected stop code pattern) of the data SCD based on the bit image from the stop code bit image memory 24 is compared with the registered stop code pattern. Then, it is determined which registered stop code pattern matches the stop code pattern. If there is a registered stopcode pattern that matches this detected stopcode pattern, the reading direction of the barcode 6 has also been determined based on this, so the data corresponding to this matched registered stopcode pattern ( The stop code data) SSC is supplied to the output data converter 33, and a conversion direction instruction signal CDD is sent to the character converter 27.

When there is no registered stop code pattern matching the detected stop code pattern SCD, the start/stop determining section 26 outputs an error signal ERR1 and supplies it to the error processing circuit 29.

The character converter 27 converts all character codes used in barcodes into bit patterns (hereinafter referred to as registered character code patterns) based on bit images obtained when correctly read in the forward direction. The bit pattern of the data CCD registered in the ROM and from the character code bit image memory 23 (hereinafter referred to as the detected character code pattern) is compared with the registered character code patterns, and matches with any of the registered character code patterns. It will be determined whether In this case, when the barcode 6 is being read in the opposite direction, the detected character code pattern CCD is reversed and compared with the registered character code pattern by the conversion direction instruction signal CDD from the start/stop determination section 26. Ru.

[0023] When the detected character code pattern CCD matches any of the registered character code patterns,
The character converter 27 outputs character data CD for the matched registered character code pattern, and sends it to the character code match comparator 28 and the output data converter 33. When the detected character code pattern CCD does not match any registered character code pattern, the character converter 27 generates an error signal ERR2 and sends it to the error processing circuit 29. Also, barcode 6 1
When all of the detected character code patterns for the scan are converted into character data CD, the character converter 27 generates a character conversion end signal CED and supplies it to the start pulse generating circuit 7 of FIG. As a result, this start pulse generating circuit 7 generates a start pulse ST,
Line sensor 10 (FIG. 2) performs the next reading scan of bar code 6.

The character code match comparator 28 receives one scan of character data CD from the character converter 27.
and compares this with the character data CD supplied from the character converter 27 in the next scan,
When all character data match, a match pulse is output and supplied to the data match counter 31. The data matching number counter 31 counts the matching pulses, and this count value is compared with the matching number set value stored in the constant memory 30 by the data matching number comparator 32. When the count value of the data matching number counter 31 exceeds the matching number setting value, the data matching number comparator 32 generates a read completion signal REND1 and sends it to the output data converter 33. If even one character data CD from the character converter 27 between the previous scan and the current scan does not match, the character code match comparator 28 outputs an error signal ERR3 and sends it to the error processing circuit 29, and also detects a data match. Clear the circuit counter 31.

The output data conversion unit 33 takes in the character data CD from the character conversion unit 27 and the stop code data SSC from the start/stop determination unit 26 every time the barcode 6 is scanned, and holds the latest data. When the read completion signal REND1 is supplied from the data matching frequency comparator 32, the character data CD and stop code data SSC held are converted into a predetermined format and sent to the host device (not shown). . At the same time, it sends a display instruction signal DIS to indicate the completion of reading to a display device (not shown) such as a lamp or buzzer, and also generates a reset signal RST to initialize itself. This reset signal RST is supplied to the reading signal latch circuit 1 (FIG. 2), etc., and resets them. When the reading signal latch circuit 1 is reset by the reset signal RST, it stops outputting the reading signal READ and stops reading the bar code 6. The illumination unit 2 is also turned off.

In this way, when the character data from the previous and subsequent scans match consecutively for a certain number of times (for example, twice) according to the predetermined number of times set in the constant memory 30, it is assumed that the barcode 6 has been read correctly and the reading ends. However, if the barcode 6 does not match this number of consecutive times, reading of the bar code 6 is repeated. However, even if reading is repeated a certain number of times, the data matching number comparator 32 does not output a reading completion signal REN.
If D1 is not output, further reading of the barcode 6 is prohibited.

That is, in FIG. 2, the scanning number counter 16 counts up by 1 each time the scanning counter 4 outputs the scanning end signal SED. The count value of the scan number counter 16 represents the number of scans of the latch sensor 10, and the scan number comparator 17 stores the number of scans in the scan number constant memory 15.
is compared with the constant set to . When the count value of the scanning number counter 16 exceeds this constant, the scanning number comparator 17 outputs a reading end signal REND2 and supplies it to the output data converter 33 of FIG.

Therefore, the output data converter 33 outputs the reset signal RST to initialize itself without sending character data or stop code data to the host device. As a result, the reading of the barcode 6 is deemed to have failed and the reading of the barcode 6 is stopped. Also,
A display instruction signal DIS indicating unreadability is sent to the display device.

The error processing circuit 29 outputs an error signal ERR.
1, ERR2, and ERR3, the character conversion reset signal CERT is output, and the count value memory control section 21 and bit image conversion section 22 of FIG. 2 and the character code bit image memory 23 and ST of FIG. The top code bit image memory 24, bit image memory control section 25, start/stop determination section 26, character conversion section 27, etc. are initialized. When the character conversion section 27 is initialized by the character conversion reset signal CERT, it outputs a character conversion end signal CED,
This causes the start pulse generation circuit 7 to generate the next start pulse ST.

As described above, the line sensor 10 reads and scans the barcode 6 multiple times, and when the character codes match consecutively a number of times equal to the number of matches set in the constant memory 30, the barcode 6 is read correctly. This character code is sent to the host device to complete the read operation.

[0031]

[Problems to be Solved by the Invention] However, the conventional touch-type barcode scanner described above has the following problems.

(1) If the barcode is crushed, chipped, voided, etc., or if the contrast is low and the quality of the barcode is poor, or if the barcode scanner's touch position on the media is not appropriate, If part of the barcode protrudes from the scanning range of the line sensor, the barcode may not be read with the correct number of digits (the number of characters the barcode has), and the barcode may be read incorrectly. A barcode scanner may not be able to detect this, and the decoded data may be sent to the host device assuming that the barcode has been read correctly.

In other words, in FIG. 3, even if a barcode with an incorrect number of digits is read, the bit image memory control section 25 will not be able to read the bit image BI enough to be supplied to the bit image converting section 22 (FIG. 2). It is written in the stop code bit image memory 24 and the character code bit image memory 23, and also written in the stop code bit image memory 24 and character code bit image memory 23.
Even if the data SCD and CCD from 23 are processed normally by the start/stop determination section 26 and character conversion section 27, even if there is an error in the contents, the data SCD and CCD are sequentially sent from the memories 24 and 23. Read out. Then, when the character code match comparator 28 outputs a match pulse the number of times determined by the number of matches set in the constant memory 30, the output data converter 33 converts the character data CD from the character converter 27 and the start stop. The stop code data SSC from the determination unit 26 is sent to the host device.

In this way, the barcode scanner does not detect the number of digits in the barcode it has read, and even if it reads a barcode with the wrong number of digits, the decoded data will be sent to the host device. . Therefore, the host device processes this decoded data, but because the number of digits is wrong, it naturally malfunctions, and as a result, it displays that there is an error in the decoded data.

When the user sees this error display, he attempts to read the barcode again, but it takes a considerable amount of time for the host device to display an error message after touching the barcode scanner to the media. This reduces the efficiency of the reading operation and places a heavy burden on the user.

(2) In order to eliminate this inconvenience, the number of digits of the barcode to be used is determined by the standard, so the number of digits of the decoded data supplied from the barcode scanner on the host device side. A method of checking has been adopted. This prevents unnecessary data processing in the host device. However, even with this method, in the barcode scanner, the output data converter 33 (FIG. 3)
While the display instruction signal DIS from the host device indicates that the bar code has been successfully read, the host device displays an error message. If there is a difference between the two displays, the user may not know which display is correct or what is the cause of the difference in display, and may become confused.

Furthermore, compared to case (1) above, the time from when the barcode scanner touches the media until the host device displays an error is shorter because the host device does not process the data. But it's quite long.

(3) In (1) and (2) above, in FIG. 3, even if the number of bit images BI written to the character code bit image memory 23 has an error in the number of digits, the number of bit images BI is equal to the number of digits×1. This is the case where the number of bars is equal to the number of bars in the character code.

However, such a case is rare, and in general, if there is an error in the number of digits, the number of bit images of the data CCD finally read out from the character code bit image memory 23 in FIG. 3 will be 1 character. less than the number of bars in minutes. In such a case, the character conversion unit 27 cannot convert this data CCD into a character, so it determines that there is no registered character code pattern for this data CCD, outputs an error signal ERR2, and starts reading the next barcode. let

If the reading of a barcode with an incorrect number of digits is repeated and this operation is repeated, incorrect decoded data will not be sent to the host device, but the constant of the scanning number constant memory 15 in FIG. Even if the barcode is read the number of times determined by , if the barcode with the wrong number of digits continues to be read, the barcode reading will finally be stopped by the reset signal RST, and the output data conversion shown in Figure 3 will occur. A display instruction signal DIS is sent from the section 33 to indicate that reading is not possible.

In the barcode scanner, no display is made until the barcode is displayed as unreadable, and the user assumes that the barcode is being read correctly during that time. In the above barcode scanner,
The pulse width of the start pulse is changed each time the line sensor scans, so that barcode reading is performed under optimal conditions. Normally, barcode reading is started and then decoded data is output to the host device and read. The time it takes to display completion is instantaneous, about 0.3 seconds. However, if it is displayed as unreadable as shown above,
It takes about 1 second for this display to appear, which is much longer than the above, which not only makes the user feel uncomfortable, but also makes it difficult for the user to read the screen if the display is unreadable after waiting for a longer time than usual. This can disrupt your rhythm and cause you to feel tired.

[0042] An object of the present invention is to provide an optical reading device that can solve this problem and quickly detect erroneous reading of a barcode with an incorrect number of digits.

[0043]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes a first means for counting bit images to detect the number of digits of a read barcode;
and a second means for comparing the detection value of the means with a reference value predetermined for the barcode and equal to the number of digits.

[0044]

[Operation] Bit images are counted to determine whether the barcode has been read with the correct number of digits, so barcodes with an incorrect number of digits can be read incorrectly before the decoding process converts the bit image into character data. Detected.

[0045]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. FIG. 1 is a block diagram showing essential parts of an embodiment of an optical reading device according to the present invention, in which 253 is a constant memory;
4 is a digit number comparator, and parts corresponding to those in FIG. 3 are given the same reference numerals and redundant explanations will be omitted. This embodiment has a front part with the same configuration as the conventional one shown in FIG. 2 and a rear part shown in FIG. 1, but since this front part has already been explained, only the rear part is shown in FIG. explain.

In FIG. 1, the bit image memory control unit 25 includes a constant memory 253 in addition to the configuration shown in FIG.
and a digit comparator 254 are added, and a constant memory 2
53 stores a constant representing the standard number of digits of the barcode.

When the barcode is read and the bit image BI is supplied, the character counter 2512 counts the number of digits of this barcode as explained in FIG. 3, but the count value memory 20 (FIG. 2) When reading is completed, the digit number comparator 254 operates and the character counter 2
The count value of 512 and the constant of constant memory 253 are compared. When these match, the digit number comparator 254 does not output the error signal ERR4, and decoding processing operations such as character conversion described in FIG. 3 are performed. Count value of character counter 2512 and constant memory 253
When the digit number comparator 254 does not match the constant, the digit number comparator 254 generates an error signal ERR4 and sends it to the error processing circuit 29. As a result, the error processing circuit 29 outputs a character conversion reset signal CERT and starts reading the bar code again.

In this way, in this embodiment, writing of the bit image BI in the bit image 23 to the stop code bit image memory 24 and the character code bit image memory 23 is completed, that is, the character conversion process is completed. The number of digits in the barcode being read is detected before the barcode is read, and it is determined whether the number of digits is correct or not, and erroneous readings of barcodes with the wrong number of digits can be detected in a short time. Become. Furthermore, in this case, character conversion is not performed, and the decoded data of the bar code resulting from such erroneous reading is not sent to the host device.

It is also possible to store constants for all the digits according to the bar code standard in the constant memory 253 in FIG.
In this case, all barcodes with this number of digits can be targeted. The digit comparator 254 sequentially compares the count value of the character counter 2512 with each constant in the constant memory 253 until a match is found, and outputs an error signal ERR4 when there is no match.

[0050]

[Effects of the Invention] As explained above, according to the present invention,
The number of digits read in a barcode can be detected before converting the bit image of the read barcode into characters, and the time required to detect misreading of a barcode with an incorrect number of digits can be greatly reduced. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing essential parts of an embodiment of an optical reading device according to the present invention.

FIG. 2 is a block diagram showing a part of an example of a conventional optical reading device.

FIG. 3 is a block diagram showing the remaining portion of FIG. 2 of an example of a conventional optical reading device.

[Explanation of symbols]

23 Character code bit image memory 24
Stop code bit image memory 25 Bit image memory control section 251 Address counter 2511 Bit counter 2512 Character counter 252 Address decoder 253 Constant memory 254 Number of digits comparator 26 Start/stop judgment section 27 Character conversion section 29 Error processing circuit

Claims (1)

[Claims] 1. A bit image representing the type of bar is generated for each bar of a barcode to be read, and the bit image is divided into a number equal to the number of bars forming the character code of the barcode. In an optical reading device configured to convert each of the classifications into character data, a first means for counting the bit image and detecting the number of character codes of the barcode to be read; and a second means for comparing the detected value of the barcode with a reference value equal to a predetermined number of character codes for the barcode, and when the detected value and the reference value do not match, the barcode is immediately detected. An optical reading device characterized in that the optical reading device performs the next reading of the image.