JPH04268982A - Optical reader - Google Patents

Abstract

PURPOSE:To read and decode only one desired bar code in an optical reader using a line sensor with scanning range extending over plural bar codes. CONSTITUTION:The Bar codes 6A, 6B are included in the scanning range of the line sensor 10, and a specific range of one bar code within the scanning range is defined in constant memory 34 as a reading range. It is decided whether or not the line sensor 10 performs scanning the reading range by comparing the count value of one scan counter 4 with data in the constant memory 34 by a comparator 35, and a switch 216 is turned on while the line sensor 10 scans the reading range by the output RRC of the comparator 35. An address counter 213 is operated by a start signal MST from a margin decision part 211 when the switch 216 is turned on, and write on count value memory 20 is performed.

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,
Although the combination pattern of thin bars differs depending on the barcode format, all formats have margins (blank spaces) and bars representing start and stop codes before and after the row of bars representing all character codes. A queue is set up.

[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 this barcode display is used as a start margin, and the part of the base color of the medium of a predetermined width on the right side of this barcode display is used as a stop margin. The margin is used to determine whether the barcode is displayed. The thin bar at the left end of the barcode display and the thin bar following it represent the start code, and the thin bar at the right end and the thick bar one position to the left represent the stop code. Then, between these start codes and stop codes, a character code is used to determine the display contents by a combination of a predetermined number of thin bars or thick bars (black bars) and thin spaces or thick spaces (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. , the stop code pattern is different, and this makes it possible to determine the reading direction of the bar code.

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. 5 and 6. 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, 211 is a margin judgment section, 212 is a first throw judgment section, 213 is an address counter , 214 is an address decoder, 215 is a reset circuit, 22 is a bit image converter, 23 is a character code bit image memory, 24 is a stop code bit image memory,
25 is a bit image memory control section, 26 is a start/stop determination section, 27 is 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 match counter, 32 3 is a data matching frequency comparator, and 33 is an output data converter.

In FIG. 5, 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. 6) 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 reads the image on the light-receiving surface one pixel each time the clock φ1 is supplied, and scans and reads the bar code 6 in response to the start pulse ST. 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 outputs the scan end signal SED.
When the clock φ1 for one scan of the line sensor 10 is counted, the scan end signal SED is output again. This scan end signal SED is sent to the start pulse generation circuit 7, the scan number counter 16, and the count value memory 2.
0, margin determination circuit 211 and address counter 2
13.

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 an address counter 213.

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.

The count value memory control section 21 includes a margin determination section 211, a first throw determination section 212, an address counter 213, an address decoder 214, and a reset circuit 215. The margin determination unit 211 calculates the count value N of the timer counter 19 for the blank area (start margin, stop margin) provided before the first bar and after the last bar of the barcode 6,
Depending on the ratio of the count value of the blank area and the barcode area,
The start and end of the barcode are detected and a start signal MST and an end signal MED are generated. Furthermore, when the start margin and stop margin are insufficient, a margin error signal MER is output and supplied to the reset circuit 215. When the scan end signal SED is supplied from the 1-scan counter 4, the margin determination circuit 211 does not operate. The first throw determination unit 212 detects the size of the count value N output from the timer counter 19, and generates a first throw error signal when the interval between edge pulses EG from the edge detection circuit 18 is too narrow or too wide. is output and supplied to the reset circuit 215. When the barcode 6 printed on the media 5 becomes narrower or wider due to smearing, scratches, or dust adhesion and is read, the first throw determination unit 212 outputs a first throw error signal. do. When the margin error signal MER is supplied from the margin determination section 211 or the first throw error signal is supplied from the first throw determination section 212, the reset circuit 215 generates a reset signal and starts counting with the address counter 213. and the value memory 20.

When the scan end signal SED is no longer supplied from the 1-scan counter 4 and the line sensor 10 starts scanning, the address counter 213 detects the margin determination unit 21.
1, the start signal MST is supplied, and the edge signal EG from the edge detection circuit 18 starts counting from the initial value. The count value output from address counter 213 is decoded by address decoder 214 and supplied to count value memory 20 as address signal ADR. The count value memory 20 enters the write mode when the scan end signal SED is no longer supplied from the 1-scan counter 4, and the count value N output from the timer counter 19 goes to the address specified by the address signal ADR of the count value memory 20. Written sequentially.

When the count value N for all bars of the barcode 6 is written into the count value memory 20 and the end signal MED is output from the margin determination section 211, the address counter 213 stops counting and the initial value is set. be done. Next, after one scan of the line sensor 10 is completed, one
When the scan counter 4 outputs the scan end signal SED, the count value memory 20 enters the read mode, and the address counter 213 outputs the count value sequentially incremented by 1 from the initial value by the internal clock. This count value becomes the address signal ADR of the count value memory 20 in the address decoder 214. Therefore, from the count value memory 20, the written count value N
are read in the order they were written.

Note that when the reset circuit 215 outputs a reset signal, the address counter 213 is reset to its initial value and the count value memory 20 is cleared. The margin determination unit 211 continues to output the margin error signal MER until the next margin determination, and the first throw determination unit 212 continues to output the first throw error signal until the next scan end signal SED is supplied from the 1-scan counter 4. continue.

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

Next, FIG. 6 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
determines whether the bit image BI is a character code bit image (character code bit image) or a stop code (stop code bit image) by determining the output order of the bit image BI. Identify and bit image BI
When is a character code bit image, the bit image BI is divided into five pieces, each of which is 1 byte of data, and these data are sequentially written into the character code bit image memory 23, so that the bit image BI becomes a stop code bit image. If so, it is written into the stop code bit image memory 24. In the case of Interleaved 2 of 5, bit images for black bars and white bars are separated, and 1 byte of data is formed for each and written to the character code bit image memory 23. When the writing in the character code bit image memory 23 and the stop code bit image memory 24 is completed, the bit image memory control section 25 sequentially reads out the 1-byte data CCD from the character code bit image memory 23 and writes the data into the character code bit image memory 23 and the stop code bit image memory 24. Also, the stop code bit image SCD is read from the stop code bit image memory 24 and sent to the start/stop determining section 26.

In the start/stop determining section 26,
For the correct stopcode used in the barcode,
A bit pattern (hereinafter referred to as a registered stop code pattern) consisting of two types of bit images obtained when correctly read in the forward and reverse directions is registered in the ROM, and two bit patterns from the stop code bit image memory 24 are stored in the ROM. The bit pattern of the image data SCD (hereinafter referred to as a detected stop code pattern) is compared with the registered stop code patterns to determine which registered stop code pattern it matches. When there is a registered stopcode pattern that matches this detected stopcode pattern, the reading direction of the barcode 6 can also be determined based on this, and the data (stopcode data) corresponding to this matched registered stopcode pattern can be determined. S
SC 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 conversion unit 27 converts all character codes used in barcodes into bit patterns (hereinafter referred to as
The registered character code pattern) is registered in the ROM, and the character code bit image memory 2
The bit pattern of the 1-byte data CCD from 3 (hereinafter referred to as the detected character code pattern) is compared with the registered character code pattern to determine which registered character code pattern it matches. In this case, when the barcode 6 is read in the opposite direction,
Conversion direction instruction signal C from start/stop determining section 26
The detected character code pattern CCD is reversely reversed by the DD and compared with the registered character code pattern.

[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 scanned detected character code patterns CCD are converted into character data CD, the character conversion section 27 generates a character conversion end signal CED and supplies it to the start pulse generation circuit 7 of FIG. As a result, the start pulse generating circuit 7 generates a start pulse ST, and the line sensor 10 (FIG. 5) performs the next reading scan of the 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. 5), 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 they do not match this number of consecutive times, reading of the barcode 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 REND.
If 1 is not output, further reading of the barcode 6 is prohibited.

That is, in FIG. 5, 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 this scanning number counter 16 represents the number of scanning of the line sensor 10, and the scanning number constant memory 15 is
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. 5 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. As a result, the character conversion section 27 outputs a character conversion end signal CED.

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] By the way, the barcode scanner using the line sensor as described above is capable of changing the registered character code pattern in the character converting section 27, thereby converting the barcode scanner used in various products. Applicable to code. Since the size of the scanning range of the line sensor on the media when the barcode scanner is touched to the media is fixed, it is possible to read barcodes that fall within this scanning range, but the size of the barcode is is not constant, and its size varies depending on how it is used. When using the same type of barcode scanner as above to read barcodes that are used in various ways, there is no problem if only one barcode falls within the scanning range of the line sensor. However, when reading a desired barcode from a list of many small barcodes, such as a TV program guide, two or more barcodes may fall within the scanning range of the line sensor, or
The scanning range of the line sensor may be set across two or more barcodes, and in such cases, the following problems occur. However, in the following description, the scanning range of the line sensor 10 in FIG. 5 is assumed to be the size of two barcodes.

(1) If you want to read a desired one of the many barcodes listed, touch the barcode scanner to the media so that the desired barcode falls within the scanning range of the line sensor. let

Therefore, if the barcode to be read is barcode A, as shown in FIG. 7, the desired barcode A is entirely within the scanning range of the line sensor 10, but the adjacent barcode B is partially There may be cases where the image falls outside of this scanning range. In such a case, as shown in FIG. 5, the line sensor 10 reads the barcode A, the margin determination unit 211 generates the start signal MST, the address counter 213 starts counting, and the barcode is stored in the count value memory 20. The count value N of the timer counter 19 for A is stored. However, next time the line sensor 10 starts reading barcode B,
The margin determination unit 211 generates the start signal MST again,
The address counter 213 starts counting, and in the count value memory 20, the count value N of the timer counter 19 for this barcode B is rewritten. but,
Since a part of the barcode B protrudes from the scanning range of the line sensor 10, this part is not rewritten in the count value memory 20. Therefore, in the count value memory 20, the count value for barcode B and the count value N for barcode A coexist.

When the count value N of the count value memory 20 is decoded by bit image conversion or character conversion as described above, an error generally occurs.
Even though the code was read so that it could be decoded correctly, a decoding error occurs.

(2) Furthermore, as shown in FIG. 8, when both barcodes A and B are within the scanning range of the line sensor 10 as a whole, the timer counter 19 for the undesired barcode B is stored in the count value memory 20. Only the count value N will be stored and decoded,
This means that the wrong barcode was read.

(3) In order to prevent this, when the address counter 213 operates in response to the start signal MST from the margin determination unit 211 and then stops in response to the end signal MED from the margin determination unit 211, the one-scan counter 4
It may be possible to respond to the start signal MST from the margin determination unit 211 only after it has been cleared by the scan end signal SED from the margin determination unit 211. according to this,
In the case of FIGS. 7 and 8, the count value N of timer counter 19 is not written to count memory 20 for barcode B, but barcode A is decoded.

However, there are cases in which the quality of the barcode A is poor due to crushing, chipping, voids, or low contrast, and the margin determination unit 211 does not generate the start signal MST even if the line sensor 10 reads the barcode A. Yes, in such a case, address counter 2
13 is not counted, and the count value N for barcode A is not written into the count value memory 20. Then, when the line sensor 10 reads the barcode B, the margin determination unit 211 generates a start signal MST, the address counter 213 starts counting, and the count value of the timer counter 19 for the barcode B is stored in the count value memory 20. The value N will be written, and the above (
The problems mentioned in 1) and (2) arise.

As explained in (2) and (3) above with respect to FIG. data will be sent,
The host device will perform erroneous processing that the user does not want. For example, a barcode may be read from a barcode television program guide as described above to make a reservation for a program. However, if a barcode like the one above is read, the order may be out of order. In this case, the host device reads and processes these character data and displays the results as they are. Therefore, the user must check this display and correct any errors, which reduces input efficiency and imposes a heavy burden on the user.

(4) In order to eliminate this inconvenience, error prevention processing has conventionally been performed on the host device side. For example, as shown in FIGS. 7 and 8, adjacent barcodes A,
B has different data such as channel number and date, and the number of digits of these characters and the letters and numbers used are different, and the character data of each data is sent in the order determined by the host device. It determines and displays whether or not it has been used.

However, according to this, although incorrect inputs and malfunctions in the host device can be prevented, the display of the output data shown in FIG. On the other hand, the host device displays a defective message, causing confusion for the user due to the difference in display.

(5) Furthermore, by the time the barcode is read and the host device displays the above display, (
It takes a long time (time from reading the barcode with the barcode scanner to decoding) + (time to transfer character data to the host device) + (time for the above judgment processing on the host device). Coupled with the situation in 3),
This disturbs the rhythm of barcode reading work, increases the user's sense of fatigue, and places unnecessary effort and psychological burden on the user.

[0042] The purpose of the present invention is to solve such problems,
An object of the present invention is to provide an optical reading device capable of quickly detecting erroneous barcode reading and reducing a user's work burden.

[0043]

[Means for Solving the Problems] In order to achieve the above object, the present invention reads a specific range the size of one barcode out of the scanning range of a line sensor that is the size of multiple barcodes. a first means for determining whether the scanning position of the line sensor is within the reading range; and a timer counter for a barcode starting from within the reading range based on the determination result of the first means. means for writing the count value of 1 to the count value memory.

[0044]

[Operation] The line sensor performs reading scanning over the entire scanning range, but by the first and second means, only the count value for the barcode whose starting point is within the reading range is stored in the count value memory. written and decoded. Therefore, by ensuring that at least the starting point of the desired barcode is located in the reading range, this desired barcode will be reliably decoded unless there is a reading error, and other undesired barcodes will take its place. It is never decoded.

[0045]

Embodiments Hereinafter, embodiments of the present invention will be explained with reference to the drawings. 1 and 2 are block diagrams showing one embodiment of an optical reading device according to the present invention, in which 6A and 6B are bar codes,
34 is a constant memory, 35 is a reading range comparator, and 216 is a switch. Portions corresponding to those in FIGS. 5 and 6 are given the same reference numerals and redundant explanations will be omitted.

In FIG. 1, the scanning range of the line sensor 10 is large enough to include n barcodes on the media 5 (n is an integer greater than or equal to 2, and hereinafter n=2). be. The reading range is the size of one barcode within this scanning range, and the upper and lower limit values of the count range of the 1-scan counter 4 when the line sensor 10 scans this reading range are the reading range setting values. Constant memory 34
is stored in.

At the start of the reading scan of the line sensor 10, the 1-scan counter 4 counts the clock φ1 from the frequency dividing circuit 11, and the count value of the 1-scan counter 4 and the reading range setting value of the constant memory 34 are the reading range. Comparator 3
5 is compared. This reading range comparator 35 becomes high level when the count value of the 1-scan counter 4 is between the lower limit and the upper limit of the reading range setting value (when the scanning position of the line sensor 10 is within the reading range), When the value is not between the upper and lower limits of the reading range setting value (line sensor 10
(when the scanning position of the scanning position is outside the reading range), a detection signal RRC that becomes low level is output. Count value memory control section 21
, the start signal MST output from the margin determination section 211 is supplied to the address counter 213 via the switch 216, but the switch 216 is controlled by the detection signal RRC from the reading range comparator 35. It is turned on when the detection signal RRC is at a high level, and turned off when it is at a low level.

Therefore, if the reading range is one barcode in the first half of the scanning range of the line sensor 10, if at least the front part of one barcode 6A on the media 5 is within this reading range, this barcode Start signal M output from margin determination unit 211 upon reading code 6A
The timing of ST is within the period when switch 216 is on, and this start signal MST is supplied to address counter 213 via switch 216. Therefore,
The address counter 213 counts the edge signal EG, and the count value N of the timer counter 19 for the entire barcode 6A is written into the count value memory 20.

In this case, the next barcode 6B is always outside the reading range, and the line sensor 10 detects this barcode 6B.
When scanning B, the switch 216 is off,
Even if the margin determination section 211 generates a start signal MST for this barcode 6B, this start signal MST is not supplied to the address counter 213.

Therefore, as shown in FIGS. 3 and 4, when the front part of the barcode 6A is within the reading range, the start signal MST from the margin determination section 211 by reading the barcode 6A is output to the switch 216. If it is in the on period, the count value N of the timer counter 19 for this barcode 6A is definitely written into the count value memory 20 and decoding processing is performed. Barcodes 6B other than barcode 6A will not be decoded regardless of whether barcode 6A is read or not.

In this way, by ensuring that at least the front part of the desired barcode to be read is within the set reading period, only the desired barcode is reliably read and decoded. Line sensor 1
Even if a plurality of zero barcodes are read and scanned, or even if there is an error in reading a desired barcode, the incorrect barcode will not be read and decoded. Therefore, barcodes are always read and decoded correctly.

[0052]

[Effects of the Invention] As explained above, according to the present invention,
Even when the line sensor reads and scans a plurality of barcodes, only the desired barcode is always read and decoded, and malfunctions such as erroneously reading and decoding other barcodes can be prevented.

[Brief explanation of the drawing]

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

FIG. 2 is a block diagram showing a portion of an embodiment of the optical reading device according to the present invention following the portion shown in FIG. 1;

FIG. 3 is a diagram showing one barcode reading operation in the embodiment shown in FIGS. 1 and 2;

FIG. 4 is a diagram showing another operation of barcode reading in the embodiment shown in FIGS. 1 and 2;

FIG. 5 is a block diagram showing a part of an example of a conventional optical reading device.

FIG. 6 is a block diagram showing a portion of an example of a conventional optical reading device following the portion shown in FIG. 5;

FIG. 7 is a diagram showing one operation of barcode reading in the conventional technology shown in FIGS. 5 and 6;

FIG. 8 is a diagram illustrating another barcode reading operation in the conventional technology shown in FIGS. 5 and 6;

[Explanation of symbols]

4 1 scan counter 5 Media 6A, 6B Barcode 10 Line sensor 19 Timer counter 20 Count value memory 211 Margin judgment section 213 Address counter 216 Switch 34 Constant memory 35 Reading range comparator

Claims (1)

[Claims] 1. A line sensor that has a scanning range for a plurality of barcodes printed on a medium and scans the scanning range to read the barcode, and a line sensor that binarizes the output signal of the line sensor. an edge detection circuit that detects the edges of the binary signal obtained by the process and generates an edge signal; a timer count that counts clocks for each edge signal and generates a count value according to the bar width of the bar code; A count value memory that stores the count value, and an optical reading device that generates character data of the read barcode by decoding the count value stored in the count value memory. A first means for determining whether or not a scanning position of the line sensor is within the reading range, with a specific range corresponding to one barcode in the scanning range of the sensor as a reading range; and a second means for writing only the count value of the timer counter for the barcode starting from within the reading range into the count value memory, which is controlled according to the result, and a plurality of barcodes included in the scanning range of the line sensor. An optical reader is capable of reading and decoding only one of the barcodes.