JPH06290294A - Bar code reading circuit - Google Patents

Abstract

PURPOSE:To provide the satisfactory bar code reading circuit which can deal with the kind of a line image sensor, the change of read picture element density or a change in the thickness of bars caused by the change of an optical system with a same circuit by setting a threshold value for deciding the thickness of respective bars with different thickness from the outside. CONSTITUTION:A line image sensor 3 to read a bar code 1 is connected to a voltage comparator 6, the voltage comparator 6 is connected to a serial-in/ parallel-out shift register 21, and image data are converted to parallel data here. Logic gates 22, 23, 24 and 25 detect the front edge and rear edge of a read pattern which reads the bars. A pattern width setting register 28 sets a value between the numbers of picture elements corresponding to the thickness of respective bars. A programmable counter 26 is provided to count the value set here, and the thickness of bars is visually recognized by comparing the width shown by this value with the width of the read pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reading circuit for reading a bar code which is printed on a passbook or the like and is composed of a plurality of bars having different thicknesses.

[0002]

2. Description of the Related Art Conventionally, bar codes have been widely used in various products. Among them, the bar code used for the passbook means a code by a combination of two kinds of bar having different thicknesses.

FIG. 4 is a circuit diagram showing a conventional reading circuit for reading a bar code of a passbook, and the conventional reading circuit will be described with reference to this figure. In FIG. 4, a reading line image sensor (CCD sensor) 3 is opposed to a barcode 1 to be read via a lens 2. A clock generator 4 and an amplifier 5 are connected to the sensor 3, and a voltage comparator 6 is connected to the amplifier 5. The voltage comparator 6 compares the output voltage of the sensor 3 amplified by the amplifier 5 with the reference voltage Vref and outputs binarized data. The voltage comparator 6 is connected to the serial-in / parallel-out shift register 7. This serial in
The parallel out shift register 7 includes a logic gate 8,
It is connected to another serial-in / parallel-out shift register 12 via 9, 10, 11.

Next, the operation will be described. First, the image of the barcode 1 is formed on each pixel of the sensor 3 via the lens 2, and the voltage corresponding to the brightness of the image of each pixel is sequentially read by the scan clock generated by the clock generator 4, After being amplified by the amplifier 5, it is compared with the reference voltage Vref by the voltage comparator 6. As a result, the read data is converted into a binary data string having several pixels of the sensor 3.

By binarizing black to correspond to "1" and white to "0", the number of transition points from "1" to "0" in the binary data string is equal to the number of bars. Become.

The magnification of the lens 2 is selected so that there are N pixels of the sensor for 1 mm of the object, and the width of the thin bar is W1 mm,
If the width of the thick bar is W2mm, the number of thin bars is W1 × N,
The thick bar is W2 × N continuous data of “1”.

The binary data string output from the voltage comparator 6 is input to the serial-in / parallel-out shift register 7. By making the clock rate of the shift register 7 equal to the scan clock, one pixel of the sensor corresponds to one bit of the shift register 7.

The output Q1 of the shift register 7 is input to the inverter 9, and the output Q2 is input to the NAND gate 10 together with the output of the inverter 9. The output of the NAND gate 10 is input to the OR gate 11. The outputs Q3 to Qn of the shift register 7 are input to the AND gate 8. The output of the AND gate 8 is input to the serial-in / parallel-out shift register 12, and the OR gate 11
Is output to the clock of the shift register 12.
With these circuit configurations, the output Q1 of the shift register 7
Is "0" and the output Q2 is "1", if all the outputs Q3 to Qn are "1", it is determined to be a thick bar, and otherwise, it is determined to be a thin bar. Here, n = (W
1 + W2) × N / 2 + 1 (rounded up after the decimal point).

When the output Q1 is "0" and Q2 is "1", the clock of the shift register 12 is enabled, and the AND signals of the outputs Q3 to Qn are input to the shift register 12, so that the thick bar is "1". , The thin bar is converted into a binary numeric data string of "0".

[0010]

In the conventional bar code reading circuit, when the type of the line image sensor or the optical system is changed and the number of sensor pixels per 1 mm of the object is changed or the bar thickness is different, , The circuit needs to be changed. In that case, the common gate array of the circuit block cannot be used, which causes a problem of increasing the cost of the circuit.

The present invention has been made in view of the above problems, and an object thereof is to make it possible to externally set a threshold value for determining the thickness of each bar having a different thickness, thereby making it possible to provide an image sensor. It is an object of the present invention to provide an excellent bar code reading circuit capable of coping with a change in the read pixel density or a change in the bar thickness due to the change of the type and the optical system in the same circuit.

[0012]

In order to solve the above-mentioned problems, the present invention reads a bar code pattern composed of a plurality of bars having different thicknesses with a line image sensor and binarizes the read image data to obtain an image sensor. In a bar code reading circuit for detecting the bar code pattern by converting the bit data corresponding to the read pixel and counting the bit, and a conversion circuit for converting the binarized image data into parallel data; A reading pattern detection circuit for detecting the leading edge and the trailing edge of the reading pattern based on the above, pattern width setting means externally set with a value between the number of pixels corresponding to the width of each bar as a threshold, and the pattern. Counting means for counting the value set by the width setting means in bits, and the reading pattern detection The number of bits corresponding to the number of pixels in the read pattern defined by the leading edge and the trailing edge detected by the circuit is the number of bits corresponding to the number of pixels set by the pattern width setting means and counted by the counting means. The comparison means is provided with a determining means for determining which bar the read pattern has.

[0013]

In the present invention having the above-mentioned structure, the image data read by the image sensor is converted into parallel data by the conversion circuit, and the leading edge and the trailing edge of the reading pattern are detected by the reading pattern detecting circuit. The leading and trailing edges detected here define the reading pattern. The pattern width setting means sets a value between the numbers of pixels corresponding to each bar of the barcode as a threshold value. This threshold can be set from the outside. The value set here is counted by the counting means, and the count value is compared with the number of bits of the read pattern by the judging means. Based on this comparison, the determination means determines which bar the read pattern has.

When the read pixel density and the bar thickness change, the pattern width setting means externally changes the threshold value for determining the bar thickness, so that it can be dealt with without changing the circuit. .

[0015]

Embodiments of the present invention will be described below with reference to the drawings. Note that elements common to the drawings are given the same reference numerals.

FIG. 1 is a circuit diagram showing an embodiment according to the present invention. In FIG. 1, similarly to the conventional example, a reading line image sensor (CCD sensor) 3 is opposed to a bar code 1 including a thick bar and a thin bar via a lens 2. A clock generator 4 and an amplifier 5 are connected to the sensor 3, and a voltage comparator 6 is connected to the amplifier 5. The voltage comparator 6 compares the output voltage of the sensor 3 with the reference voltage Vref and outputs binarized data. The voltage comparator 6 includes a serial-in / parallel-out shift register 2
Connected to 1. The clock generator 4 is also connected to the serial-in / parallel-out shift register 21.

The output Q1 of the serial-in / parallel-out shift register 21 is connected to one input terminal of the NOR gate 22 and the AND gate 23, and the output Q2 is connected to the other input terminal of the NOR gate 22 and one input terminal of the NOR gate 24. Has been done. Output Q3 is NOR gate 2
4 and the one input terminal of the NAND gate 25. The output of the NOR gate 22 is connected to the other input terminal of the NAND gate 25, and the output of the NOR gate 24 is connected to the other input terminal of the AND gate 23. The output of the AND gate 23 is connected to the programmable counter 26, and the NAND gate 25
Is connected to one input terminal of the OR gate 27.

The pattern width setting register 28 is data indicating an intermediate value (threshold value) between the number of pixels of the image sensor corresponding to the width of the thick bar of the barcode to be read and the number of pixels corresponding to the width of the thin bar. Is set. This data is loaded into the programmable counter 27.
The programmable counter 27 counts based on the loaded data and serially outputs the output signal.
Output to the parallel out shift register 29. The output of the OR gate 27 is connected to the serial-in / parallel-out shift register 29.

Next, the operation of this embodiment will be described with reference to the time chart shown in FIG. FIG. 2 is a time chart showing the operation of the embodiment.

First, the image of the bar code 1 is formed on each pixel of the sensor 3 through the lens 2, and the voltage corresponding to the brightness of the image of each pixel is sequentially read by the scan clock generated by the clock generator 4. After being outputted and amplified by the amplifier 5, it is compared with the reference voltage Vref by the voltage comparator 6. As a result, the read data is converted into a binary data string having several pixels of the sensor 3.

By binarizing black to "1" and white to "0", the number of transition points from "1" to "0" in the binary data string is equal to the number of bars. Become.

The magnification of the lens 2 is selected so that the sensor has N pixels for 1 mm of the object, and the width of the thin bar is W1 mm.
If the width of the thick bar is W2mm, the number of thin bars is W1 × N,
The thick bar is W2 × N continuous data of “1”.

The binary data string output from the voltage comparator 6 is a serial-in / parallel-out shift register 21.
Entered in. By setting the clock rate of the shift register 21 to be equal to the scan clock,
A pixel corresponds to 1 bit of the shift register 21. The outputs Q1, Q2, Q3 of the shift register 21 are shifted by one bit as shown in FIG.

The output Q1 of the shift register 21 is "1",
When Q2 is "0" and Q3 is "0", the programmable counter 2 is operated by the NOR gate 24 and the AND gate 23.
The loading signal of 6 becomes "1", the data set in the pattern width setting register 28 is loaded, and the countdown is started in synchronization with the scan clock and the clock of the shift register 21. In FIG. 2, the count value is shown as n. When the count value becomes 0, the programmable counter 26 outputs a borrow signal to the shift register 29. This borrow signal is held until the next data is loaded.

The output Q1 of the shift register 21 is "0",
When Q2 is "0" and Q3 is "1", one input of the OR gate 27 becomes "1" by the NOR gate 22 and the NAND gate 25, and the clock signal is input to the shift register 29. This clock signal enables the shift register 29, and the data at the data input terminal is taken into the shift register 29.

At this time, the data strings "001" and "100"
If the number of data from "1" to "1" sandwiched between and is greater than or equal to the numerical value (n) set in the pattern width setting register 28, that is, while the borrow signal is being output, the shift register When the clock of 29 is enabled, the data input to the shift register 29 becomes "1",
If the value is equal to or less than the set numerical value (n), that is, if the clock of the shift register 29 is enabled before the borrow signal is output, the data input to the shift register 29 becomes "0", as shown in FIG. As shown, it can be converted into a binary numerical data string in which the thick bar is "1" and the thin bar is "0".

In the present embodiment, the isolated "0" as shown by point a in FIG. 2 is regarded as noise, and is read as "1" to determine the pattern width.

In the above-described embodiment, the case where the bar has two thicknesses has been described, but the present invention can be implemented even when the bar has three thicknesses. In this case, a pattern width setting register, a programmable counter, and a serial-in-parallel-out shift register are added respectively, and two thresholds (n1, n2, but n1) that differ depending on the two pattern width setting registers are used.
<N2) is set, as shown in FIG. 3, the narrowest width is enabled if both are enabled during counting, the middle width is enabled if only n2 is enabled during counting, and then enabled after both counts are completed. If so, the width is determined to be the widest. 3 is a time chart showing another embodiment of the present invention.

Further, the present invention is also effective when reading a bar code in which the width of the white bar between the black bars is changed.

[0030]

As described above in detail, according to the present invention, the threshold value for determining the pattern width can be set from the outside by the pattern width setting register. Therefore, the type of the image sensor, the lens magnification, and the bar The threshold value can be changed according to the thickness, and various applications can be supported without changing the circuit. Therefore, cost reduction can be expected by using a common gate array.

[Brief description of drawings]

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

FIG. 2 is a time chart showing the operation of the embodiment.

FIG. 3 is a time chart showing another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a conventional barcode reading circuit.

[Explanation of symbols]

 1 Bar Code 3 Line Image Sensor 6 Voltage Comparator 21 Serial In-Parallel Out Shift Register 22 NOR Gate 23 AND Gate 24 NOR Gate 25 NAND Gate 26 Programmable Counter 28 Pattern Width Setting Register 29 Serial In-Parallel Out Shift Register

Claims (1)

[Claims] 1. A bar code pattern consisting of a plurality of bars having different thicknesses is read by a line image sensor, the read image data is binarized and converted into bit data corresponding to the read pixels of the image sensor, and the bits are converted. In a bar code reading circuit for detecting a bar code pattern by counting, a conversion circuit for converting the binarized image data into parallel data, and reading for detecting a leading edge and a trailing edge of a reading pattern based on the parallel data. A pattern detection circuit, a pattern width setting means that can be externally set using a value between the number of pixels corresponding to the width of each bar as a threshold value, and a counting means that counts the value set by the pattern width setting means in bits. And a reading defined by the leading edge and the trailing edge detected by the reading pattern detection circuit. By comparing the number of bits corresponding to the number of pixels in the read pattern with the number of bits corresponding to the number of pixels set by the pattern width setting means and counted by the counting means, it is possible to determine which bar the reading pattern has. A bar code reading circuit provided with a judging means for judging.