JPH087772B2 - Code reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention scans and reads a code (for example, a bar code display) displayed on a medium with a photoelectric converter or the like, and calculates the information shown by the code. The present invention relates to a code reader that decodes and outputs a signal that can be processed by, and particularly relates to a code reader that has an improved reading and decoding probability.

[Conventional technology]

This type of code reader photoelectrically converts codes displayed in various code systems on a medium such as a form or article surface into a signal that can be processed by a computer such as a microprocessor, by photoelectrically converting it with a scanner such as an optical reader. It decodes and outputs.
The codes to be displayed include special display codes such as bar codes and carla codes and general characters, and a certain standard is given to the display method for decoding these. This standard defines the display interval and display range. For example, for bar codes, Japanese Industrial Standards [JIS X 0502] (April 1987)
Issued on the 30th, 1st printing) Items listed on pages 3-9,
Some are specified on page 8 of American National Standard [ANSI: MH10.8M-1983]. These displays are not limited to the pen type among the typical optical scanning devices as scanners, but also the self-scanning type hand
Both the wand model and the stationary type have a significant difference in the scanning speed compensation range with respect to the bar code display part, but the display environment changes significantly, making it difficult to judge the start of the code and the decoding probability decreases. Tend to do.

In the prior art, the space immediately before the barcode is a certain distance (a distance larger than the wide space width).
When it is detected for more than a certain time (more than the count time of wide space width) for a certain time or more, it is judged that the barcode has started, so the space immediately before the barcode is more than a certain distance or more than a certain certain time. Will be required. Therefore, it is difficult to increase the density of barcode display, and there is a high possibility that the space will become dirty.
It becomes easy to malfunction.

In addition, when the count value of the bar or space that is the code element (element) is larger than a certain constant value, the decoding operation is controlled by considering it as the end of the bar code, so the scanning margin of the bar code reader causes a stop margin. Required space / bar width changes. For this reason, it is necessary to increase the stop margin width in order to correspond to the quick scan speed, and it is difficult to increase the density of the bar code display, and it is highly possible that the margin portion is stained and malfunctions occur. Easy to get up.

As a countermeasure, the start margin and the stop margin are determined by comparing the immediately preceding count value with a certain constant value or a value obtained by multiplying a certain constant to determine the start margin and the stop margin. It has been proposed that the width of the bar or the space of the bar code itself can be narrowed to increase the density and the reading error can be reduced while the bar width can be set to the minimum required limit.

FIG. 5 is a block diagram showing the configuration of the above-mentioned prior art, in which 101 is a photoelectric conversion unit, 102 is a first space detection unit, 103 is a first edge detection unit, 104 is a counter unit, 106 is a stop determination unit, 107 is a decoder section, 108 is a fast bar / space determination section, 109 is a start determination section, 7 is a second edge detector, and 11, 21, 22, 27, 31, 39, 40 are switching elements.

First, the photoelectric conversion unit 101 reads a code such as a bar code with the photoelectric converter 1, and outputs the read signal via the signal line a 2
It is supplied to the binarization circuit 2, converted into a binary level signal of "0", "1"("H","L"), and the converted signal is supplied to the switch 3.

The switch 3 is initially connected to the x side in the figure by the reset signal, and is switched to the y side in the figure by the signal of the signal line e. Therefore, the switch 3 connects the signal line b to the space detector 4, and gives an output to the signal line e when the signal on the signal line c is a signal corresponding to the space (for example, "L"), 3 to y
Switch to the side. As a result, the signal b on the output line of the photoelectric conversion unit 101 passes through the switch 3 and enters the switch 5 from the signal line d. Since the switch 5 is placed on the x side by the reset signal, the signal line d is connected to the first edge detector 6 via the signal line f.

The first edge detector 6 detects when the signal from the signal line f changes from the space to the bar (“L” → “H”) or when the signal changes from the bar to the space (“H” → “L”). It is detected and the output is given to the signal line h. The edge detection signal on the signal line h switches the switch 5 to the y side and enters the first counter 8 of the counter section 104, and this signal causes the first counter 8 to move.
Sets the count value to 0 and starts the counting operation of the clock CL. The first counter 8 receives the reset signal,
Similarly, by inputting a signal on the output line i of the second edge detector 7, which will be described later, 0 is cleared, counting is started, and the count value is sent out on the signal line j. This first counter 8
When the overflow value set in the first constant register 9 is compared with the overflow comparator 10, and the counter overflows (for example, when scanning is stopped in the middle), the overflow comparator 10 outputs a reset signal. To be done.

Now, the second edge detector 7 inputs the signal from the photoelectric conversion unit 101 via the switches 3 and 5 based on the first edge detection of the first edge detector 6 and outputs the signal on the input signal line g. When the signal changes (“H” → “L” or “L” → “H”), the detection signal is supplied to the first counter 8 through the signal line i, and at the same time, the second counter circuit of the fast bar / space determination unit 108. Give to 28.

The fast bar / space determination unit 108 counts the sum of the bar and space after detecting the fast bar (second
The contents of the counter circuit 28), when a number preset in the fourth constant register 29 is reached, a signal is output to the signal line C (the number of spaces and bars for start determination is counted).

The second counter circuit 28 sequentially increments the counter by the signal from the signal line i and sends the count value to the signal line A. Note that the counter is cleared to 0 by the reset signal. A sum (two or more) of the number of bars and spaces used for determining the start of the bar code is preset in the fourth constant register 29, and the value is sent to the first margin comparator 30 via the signal line a. The comparator 30 compares the count value from the signal line A with the value from the signal line A, and the count value is the fourth value.
Outputs a signal on the signal line c when the value is equal to or greater than the value set in the constant register.

The switch 31 sends the signal from the second edge detector to either the start determiner 109 and the switch 39 or the stop determiner 106 and the switch 21. This switching is performed by the reset signal and the output signal of the fast bar / space determination unit 108. Then, when the reset signal is input, x from the y side
When a signal is input to the side from the signal line c, the x side is switched to the y side.

The switch 11 is activated by the signal from the first edge detector 6 and sends the count value from the counter unit 104 to the start determination unit 109 and the stop determination unit 106.

The start determination unit 109 compares the count value of at least the first bar and the space and compares the count value of the space or bar (content of the first counter memory 12) with the count value of the immediately preceding space or bar (second previous counter memory). When the number of times exceeds a certain constant (content of 35) (content of sixth constant register 36), a reset signal is sent to the signal line server. That is, at the start determination, the count value of at least the first bar and the space are compared without looking at the start margin, and when it is determined that the start is not started, the reset signal is output.

Further, the first counter memory 12 stores the count value from the signal line 1 and sends it to the signal line m. And
The stored count value is reset by the reset signal.

A count value larger than (wide bar or space / slow scan speed) is preset in the fifth constant register 33, and the value is given to the signal line counter. Only when the reset signal is input, the signal line counter is set. It is stored in the second previous counter memory 35 via the switch 34 that connects the signal line and the signal line. The stored count value is given to the second multiplier 37 via the signal line and is larger than the value set in the sixth constant register 36 by the second multiplier 37 (wide bar or space / narrow bar or space). Is multiplied by the value. The multiplication result is supplied to the third margin comparator 38 via the signal line C.

The third margin comparator 38 outputs the output signal (count value) of the first counter memory 12 from the signal line m and the second multiplier.
The multiplication output value of 37 is compared, and when the count value is equal to or more than the multiplication output value, a signal is output on the signal line circuit.

When the reset signal (i) is input, the switch 40 connects the signal line terminal and the reset line and outputs the signal from the signal line terminal as the reset signal. Further, (ii) when a signal from the signal line C (output signal of the fast bar / space determination unit 108) is input, it operates to disconnect the signal line server and the reset output line. The switch 32 connects the signal line m and the signal line k only when a signal from the signal line D is input, and supplies the stored value of the first counter memory 12 to the second previous counter memory 35. In other cases, the signal line m and the signal line key are separated.

Further, the switch 39 connects the signal line m and the signal line t only when the signal from the signal line D is input, and the switch 39 is connected to the first counter memory.
The value of 12 is supplied to the decoder unit 107.

The switch 39 and the switch 21 are operated by the signal from the second edge detector 7, and the switch 39 uses the count value of the bar or space from the first counter memory 12 as described above, and the switch 21. 21 is a second counter memory as described later.
The count value of the bar or space from 15 is sent to the decoder unit 107, respectively.

Further, the switch 27 is operated only when a signal is input from the signal line C, that is, by a signal from the fast bar / space determination unit 108, and a signal from the signal line m is transferred to the signal line p.
The count value of the final bar or space used for the determination in the start determination unit 109 is guided to the stop determination unit 106.
To the first previous counter memory 17 of.

 Next, the operation of the stop determination unit 106 will be described.

The stop determination unit 106 uses a constant (third constant) of the count value of the bar or space currently being read, that is, the content of the second counter memory 15 is the count value of the immediately preceding space or bar, that is, the content of the previous counter memory 17. When the value exceeds the value set in the register 18) times, it is sent to the signal line u. The second counter memory 15 receives the signal from the signal line 1, that is, the first counter circuit 8 of the counter section 104.
The count value of is stored and sent to the signal line o. The switch 16 connects the signal line o and the signal line p to the value of the second counter memory 15 only when the signal from the signal line O, that is, the output signal of the second edge detector 7 through the switch 31 is input. Is sent to the first previous counter memory 17. The first previous counter memory 17 stores the signal from the signal line p and gives the value to the first multiplier 19 via the signal line q. A value larger than the (wide bar or space / narrow bar or space) of the bar code is preset in the third constant register 18, and this set value is given to the first multiplier 19 via the signal line r, Multiply the value stored in the counter memory last time,
The signal is output to the second margin comparator 20 via the signal line s.

The second margin comparator 20 compares the value of the second counter memory 15 input via the signal line o with the multiplication output of the first multiplier 19, and outputs the value from the second counter memory 15, that is, the counter unit 104. The count value of the first counter circuit 8 of
When the output value of the multiplier 19 or more, the comparison output is sent to the signal line u.

The switch 22 that receives the output of the stop determination unit 106
When the reset signal is input, the signal line u and the signal line v are disconnected,
The signal line u and the signal line v are connected by the output signal from the fast bar / space determination unit 108 from the signal line c. That is, the output signal from the stop determination unit 106 is applied to the decoder unit 107 from the time when the first stop bar / space determination signal (start margin determination signal) from the first fast bar / space determination unit 108 is input, and the decoder operation is controlled.

The decoder unit 107 decodes the meaning of the code element of the bar code based on the count value of the clock CL corresponding to the width of the bar or space of the bar code that has been read. Have

The function of each block constituting the illustrated decoder unit 107 is as follows.

The bit image converter 23 operates by the detection output of the second edge detector 7 from the signal line i, converts the count value input from the signal line t into a bit image, and outputs the bit image memory 24 via the signal line w. To memorize. If an error occurs during this conversion, a reset signal is output. The bit image memory 24 (i) stores the bit image from the signal line w, and (ii) sends the bit image stored by the signal input from the signal line v to the character converter 25 via the signal line x. Yes, (iii) When the reset signal is input, the stored bit image is cleared and each operation is performed.

The charactor converter 25 starts its operation by the signal input from the signal line v, converts the bit image coming from the bit image memory 24 into charactor, and supplies it to the output circuit 26 via the signal line y. If an error occurs during character conversion, a reset signal is output.

Then, the output circuit 26 sends the charactor signal from the signal line y to the output line z and supplies it to the display means (not shown).
Upon completion of this transmission, the reset signal is output.

In the above configuration, in order to judge the start margin and the stop margin, the count value of the current bar or space due to the scanning of the bar code is multiplied by the constant value of the previous space or bar count value. I'm comparing. That is, since the start and the stop are determined in relation to the current count value and the immediately preceding count value, the width of the space (start margin, stop margin) installed before and after the display code can be made small. Moreover, since the width of the bar or the space forming the code does not depend on the scanning speed of reading, the code display can be made highly dense. For this reason, the probability that dirt is attached to the code display is reduced,
Occurrence of malfunction is reduced.

[Problems to be Solved by the Invention]

In the above-mentioned prior art, since the stop determination is performed at a constant multiple of the count value of the last bar or space, if the last bar or space is a wide bar or wide space, the narrow bar or narrow space is determined. The stop judgment distance that is more than twice that of the space is required.

FIG. 6 is an explanatory diagram of an example of the stop determination operation according to the prior art, in which (a) is a bar code and B _N is a narrow bar.
B _W is the wide bar, and C is the scanning direction. Further, (b) is a waveform diagram obtained by scanning the barcode of (a), where t _A is the count value of the narrow bar B _N , t _B is the count value of the weight bar B _W , and A is a constant.

As shown in the figure, in the conventional configuration shown in FIG. 5, when the final bar or space (wide bar B _{W in} the figure) of the bar code is multiplied by a certain constant (A), the stop occurs. It is a judgment.

Therefore, the margin for the stop determination (stop margin) cannot be less than or equal to that corresponding to the count value of the wide bar or the wide space, and the margin space for the code display cannot be further reduced. Can not.

It is an object of the present invention to provide a code reading device capable of setting a minimum margin space required for stop determination regardless of the size of the bar or space of the read code.

[Means for solving the problem]

The above object is to provide a minimum count value storage means for storing the count value corresponding to the minimum bar or the minimum space in the read code, and means for comparing the current count value with a value obtained by multiplying the minimum count value by a certain constant. And is configured to determine that the code has ended when the current count value is large.

[Action]

Since the stop determination is performed based on the minimum count value in the code reading process, it is necessary to set a wide stop margin on the assumption that the last bar or space of the code is a wide bar or space as in the conventional technique. There is no.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a code reading apparatus according to an embodiment of the present invention, in which a stop determining unit 106 includes a second counter memory 15, a switch 16 and a first previous counter memory 18, Is a third constant register, 19 is a first multiplier, 20 is a second margin comparator, 42 is a seventh constant register, 43 and 44 are switchers, 45 is a minimum value counter memory, and 46 is a minimum value comparator. . Further, the same reference numerals as those in FIG. 5 correspond to the same parts, and the other configurations are the same as those in FIG. 5 except for the stop determination unit 106.

In the figure, the binary signal from the photoelectric conversion unit 101 is first supplied to the first space detection unit 102, and after the first space is detected, the first bar or space of the bar code is detected, that is, the first edge. Is detected by the first edge detection unit 102. When the first edge is detected, the switch 5 is switched, and the second edge detector 7 detects the next edge, that is, the change point of the bar or space. The fast bar / space determination unit 108 uses the second counter circuit 28 to calculate the sum of the bar and the space after detecting the fast bar.
When the sum is reached and the set number set in the fourth constant register 29 (the number of spaces and bars for start judgment: 2 or more) is reached, the switch 31 is switched to switch from the second edge detector 7. Is sent to the stop determination unit 106. The switch 31 sends the signal from the second edge detector 7 to the start determination unit 109 in response to the reset signal. The start determination unit 109 compares at least the count value of the first bar and the count value of the space, and the count value of the space or bar (content of the first count memory 12) is the count value of the space or bar immediately before (the second previous counter). The output from the third margin comparator 38 is output to the switching unit 40 when the value is larger than a certain constant A (contents of the memory 35) (contents of the sixth constant register 36). The first counter memory 12 stores the count value from the counter unit 104 and sends it from the switch 32 to the second previous counter memory 35 and the third margin comparator 38. Fifth constant register 33 (wide bar or space / slow scan speed)
That is, a count value larger than the count value of the wide bar or the wide space with respect to the assumed minimum speed of the scanning speed of the photoelectric conversion unit is preset, and when the reset signal is input to the switch 34, the count value is set to the second previous value. It is stored in the counter memory 35. The stored count value is multiplied by the second multiplier 37 with a value larger than (wide bar or space / narrow bar or space) set in the sixth constant register 36 and supplied to the third margin comparator 38. .
The switch 39 supplies the value of the first counter memory 12 to the decoder unit 107 when the switch 31 is switching to the x side. In addition, the switching unit 21 includes the stop determination unit 10 as described later.
The count value of the bar or space from the second counter memory 15 of 6 is sent to the decoder unit 107, and the switching unit 27 is used for the start determination in the start determination unit 109 when the fast bar / space determination unit 108 outputs. The final count value of the final bar or space is supplied to the first previous counter memory 17 of the stop determination unit 106 (described later).

Since the operation of the above configuration is the same as that described in FIG. 5, detailed description thereof will be omitted.

The embodiment shown in FIG. 1 is different from the prior art shown in FIG. 5 in the configuration and operation of the stop determination unit.

 The configuration and operation of the stop determination unit 106 will be described below.

The stop determination unit 106 determines that the count value of the currently read bar or space (contents of the second counter memory 15) is a constant having the minimum count value of the bars or spaces read so far (content of the minimum value counter memory 45). When it becomes B times (contents set in the third constant register 18) times or more, a stop determination output is given to the signal line u from the second margin comparator 20. A value larger than the count value of (wide bar or space / slow scan speed) is preset in the constant register 42, and when the switch 43 is operated by the reset signal, this value is set to the minimum value counter memory.
Remember in 45. The minimum value comparator 46 compares the count value of the first previous counter memory 17 with the value stored in the minimum value counter memory 45, and the value of the first previous counter memory 17 is smaller than the value of the minimum value counter memory 45. At this time, the switch 44 is operated to store the value of the first previous counter memory 17 in the minimum value counter memory 45. That is, the minimum value counter memory 45 stores the minimum count value of the bar or space that has been read so far.

Figure 2 an alien in illustration of Sutotsupu determination operation by the configuration of FIG. 1, (a) represents S _N is narrow space bar code, B _W is wide bars, C is a scanning direction. Also,
(B) is a waveform diagram obtained by scanning the barcode of (a).
t _A is the count value of narrow space (minimum space) S _N ,
t _B is a count value of the wide bar B _W , and B is set to a certain constant (wide bar or space / narrow bar or space).

As shown in the figure, since the stop determination is performed at a time when the minimum count value of the code element that has been read so far (in this case, the minimum count value of the slow space) becomes a constant B times, In the case of using the count value of the final bar or space as described above, assuming that the final code element is a wide bar, a stop margin of a certain constant A times or more of this wide bar must be secured. There is no restriction that it does not happen, and the entire space of the code can be made small.

Further, according to this structure, when the code area is dirty, a reset signal is issued as an error and the decoding is prohibited. However, it is not preferable from the standpoint of usability to make an error for fine dirt each time as well, because it lowers the reading probability.

Hereinafter, an embodiment will be described in which such a fine stain is not regarded as an error but is ignored and the reading probability is increased.

FIG. 3 is a block diagram of an essential part for explaining another embodiment of the present invention, and shows the configuration of the second edge detector 7 portion in FIG.

In the figure, 701 is an edge detector, 702 is a switch, and 70
3 is an edge detection register, 704 is an edge detection register determiner, 705 is a counter circuit, 706 is a constant memory, 707 is a comparator, and 708 and 709 are OR circuits.

The edge detector 701 is connected to the signal line terminal only when the signal from the signal line g, that is, the output signal of the photoelectric conversion unit 101 in FIG. 1 changes to “H” → “L” or “L” → “H”. Send a signal. When the reset signal is input through the OR circuit 708, the switch 702 sends the edge detection signal from the edge detector 701 from the signal line terminal to the signal line CH, and the edge detection register 703.
The edge detection signal to the counter circuit 705
As a start signal to start the clock count of the counter circuit 705 and switch the switch 702 to the signal line side. The edge detection register determiner 704 operates when a signal comes from the signal line D, and outputs an output signal to the signal line i only when the edge detection register 703 is set. The edge detection register 703 is reset by a signal from the signal line.

The counter circuit 705 stops the counting operation by setting the counter to 0 by the reset signal input through the OR circuit 709 or the signal from the output signal line D of the comparator 707, and stops the counting operation as described above. Clock signal by input
The CL counting operation is started, and its content is given to the comparator 707 via the signal line. On the other hand, in the constant memory 706, (narrow bar or space / maximum scanning speed), that is, a count value of the minimum bar or space with respect to the expected maximum scanning speed of the photoelectric conversion unit, or a smaller value is set, This value is given to the comparator 707 through the signal line and is compared with the count value from the signal line. As a result of the comparison, when the count value of the counter circuit 705 exceeds the set value of the constant memory 706, the comparison output is sent to the signal line d.

The comparison output on the signal line 2 is set by the counter circuit 705 to stop the counting operation, the content is set to 0, the switch 702 is switched to the signal line side, and the edge detection register determiner is set. To operate. That is, if an edge is detected again within a certain count (value of the constant memory 706) after the edge is first detected, the edge detection register is reset, and then the signal from the signal line D is used. Even if the edge detection register determiner operates, the edge detection signal is not output from the signal line i.

By configuring the second edge detector 7 of FIG. 1 as described above, the value set in the constant memory 706, that is,
A stain having a value smaller than the count value of the minimum bar or space with respect to the maximum scanning speed expected for scanning of the photoelectric conversion unit of the code reading device will be ignored.

FIG. 4 is a diagram for explaining the operation of the configuration shown in FIG.
Is a bar code, B _N and B _W are bars, S _N and S _W are spaces, C is a scanning direction, and P is fine dirt. Further, (b) is a waveform diagram obtained by scanning the barcode in (a), and t _P represents a count value for the stain P.

The counter circuit counts the clock CL and gives the count value of t _P due to the stain P on the bar code shown in FIG. When the count value does not exceed the value set in the constant memory 706 of FIG. 3, the edge detection due to the dirt P is reset.

As a result, it is possible to reduce the occurrence of errors due to fine dirt, reduce unnecessary errors, and improve the reading probability.

〔The invention's effect〕

As described above, according to the present invention, it is possible to reduce the stop-stop memory for stop determination, improve the reading probability, and provide a code reading device having an excellent function except for the above-mentioned drawbacks of the prior art. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is an operation explanatory diagram of FIG. 1, FIG. 3 is a main part block diagram showing another embodiment of the present invention, and FIG. Operation explanatory drawing of FIG. 3, 5th
FIG. 6 is a block diagram for explaining the prior art, and FIG. 6 is an operation explanatory diagram for FIG. 101 ... Photoelectric conversion unit, 102 ... Fast space detection unit, 103 ... First edge detection unit, 104 ... Counter unit, 10
6 ... Stop determination unit, 107 ... Decoder unit, 108 ... Farst bar / space determination unit, 7 ... Second edge detector.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Hiroaki Sasaki 1-7 Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (56) References JP-A-58-3073 (JP, A) JP-A-SHO 59-136872 (JP, A) JP-A-58-221467 (JP, A)

Claims (1)

[Claims] 1. A photoelectric conversion unit for reading a code displayed on a medium, a counter unit for counting a time corresponding to a change of a binary level signal output from the photoelectric conversion unit with a clock signal, and this counter unit. Output from the counter section, a start determination section for making a read start determination based on the count value output from the counter, a stop determination section for making a read stop determination based on the count value output from the counter section. In the code reading device including a decoder unit that decodes the count value, the stop determination unit includes a minimum count value storage unit that stores the minimum count value of the code elements that have been read so far, and a minimum count value storage unit. A comparison means for comparing the stored minimum count value with a certain constant and a current count value is provided. Code reading apparatus when the count value of the code element read current from the constant multiple value is the count value is large and characterized by being configured so as to determine that the end of the code.