JPH01116776A - Optical reader - Google Patents

Abstract

PURPOSE:To decide a start even when a start margin is short by deciding the start according to the numerical relation between a counted value whose count is started by a counting means and a counted value counted between edges according to the width of an immediately preceding code. CONSTITUTION:According to the numerical relation between the counted value whose count is started by the counting means 6 and the counted value counted between the edges according to the width of the immediately preceding code, the start is decided and if it is improper, a reset signal is applied to a decoding means. Namely, if the counted value according to the improper code is read to the decoding means, it is immediately reset, the counted value is newly reread and the reading probability of information read to the decoding means is high. A decision whether the start is proper or improper is not influenced by scanning speed for reading the code by a detecting means but the decision is executed in a time according to the scanning speed. Thereby, a narrow space as the start margin is satisfactory.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention scans and reads a code displayed on a medium (for example, a bar code display) with a photoelectric converter, and converts the information represented by the code into a computer. The present invention relates to an optical reading device that decodes and outputs a signal that can be processed by a computer, and particularly relates to an optical reading device that improves the probability of reading and decoding.

(Prior art) Optical reading devices photoelectrically convert codes optically displayed in one code system on a medium such as a form or the surface of an article, and decode it into a signal that can be processed by a computer such as a microprocessor. and output it. The displayed codes include special display codes such as bar codes and Carla codes, as well as general characters, and in order to decipher these codes, certain standards must be set for the display method.

This standard includes regulations regarding display intervals and display ranges. For example, for bar codes, Japanese Industrial Standards [JIS]
X 0502] (first printing issued on April 30, 1985), those listed on pages 3 to 9, and Ameri
can National 5 standard [A
NSI MHIo, 8M-1983], page 8, etc. These displays are not only pen-type but also self-scanning type hand wand models and stationary types among optical reading devices. However, the display environment changes significantly, making it difficult to determine the start of the code, and the probability of decoding tends to decrease. As a typical example of such an optical reading device, a conventional optical reading device for a bar code reader will be explained with reference to FIGS. 3 and 4. FIG. 3 is a block circuit diagram of a conventional optical reading device for a bar code reader, and FIG. 4 is a diagram explaining the operation of the device shown in FIG.

In FIG. 3, codes alternately displayed on the medium in two states: a space with high light reflection efficiency and a bar with high light absorption rate are detected by the photoelectric converter 1, and an electrical signal of a predetermined voltage level is detected. The binarization circuit 2, which is a detection means, indicates that, for example, a white space with a high light reflectance is at a low level (hereinafter referred to as "L"), and a black bar with a high light absorption rate is at a high level (hereinafter referred to as "L"). (hereinafter referred to as "H") is converted into a binary signal as a read signal. This binarized signal is applied to the edge detection circuit 4 via the normally open first switch 3 and also to the fall detection circuit 5.

This falling detection circuit 5 detects when the output of the binarization circuit 2 changes from "H" to "L" due to the fact that the photoelectric conversion circuit 1 is opposed to the white background of the start margin provided immediately before the bar code.
Detects the edge that is switched to and outputs a short pulse-shaped edge detection signal. This edge detection signal is applied to the counting circuit 6 to reset it and start counting the incoming clock, and is also applied to the first self-holding circuit 7 to set the self-holding state. Due to the set state of the first self-holding circuit 7, the first switch 3
is closed a little later than the edge detection signal. By closing the first switch 3, the edge detection circuit 4, which is an edge detection means, detects whether the binary signal outputted from the binarization circuit 2 goes from "L" to "H" and from "H" to "L". ” and outputs a short pulse-shaped edge detection signal. This edge detection signal from the edge detection circuit 4 is applied to a counting circuit 6, which is a counting means, to reset it and start counting, and is also applied to a normally closed second switch 8 and a normally open third switch 9. and is further applied to the second self-holding circuit 1O to set the self-holding state. Due to this set state of the second self-holding circuit IO, the third switch 9 is closed with a slight delay, and the subsequent edge detection signal is applied to the bit image conversion circuit 11. Further, a count value obtained by counting the clocks that come in between the edge detection signal and the next edge detection signal by the counting circuit 6 is provided to the comparison circuit 12 and the bit image conversion circuit 11. Also, when the counting circuit 6 overflows, the reset signal is sent to the reset line 13.
The counter circuit 6 itself is reset. In addition,
At this time, the counting circuit 6 does not start counting. Also,
Another reset signal (not shown) is supplied to the reset line 13 when the power is turned on and for resetting the counting circuit 6 by an external reset means. Comparison circuit 12 compares the count value with a constant value stored in advance in constant circuit 14, and outputs a signal when count value≧constant value. This signal is transmitted to the image signal via the fourth switch 15 which is always open.
It is applied as a decode signal to the character conversion circuit 16, and is also applied to the third self-holding circuit 17 to set the self-holding state. Due to this set state of the third self-holding circuit 17, the second switch 8 is opened slightly later than the signal from the comparator circuit 12, and the fourth switch 15 is closed slightly later than the signal. When the second switch 8 is closed, the edge detection signal output from the edge detection circuit 4 is applied to the reset line 13 as a reset signal. The bit/image conversion circuit 11 reads the counter value based on the edge detection signal applied via the third switch 9, converts it into an image signal, and outputs the image signal to the image/character conversion circuit 16. The image/character conversion circuit 16 converts the image signal into a character signal, uses the signal applied via the fourth switch 15 as a decode signal, and outputs the character signal to the output circuit 18. This image/character conversion circuit 16 is -
, if the image signal cannot be converted to a character signal,
At the same time as outputting the reset signal to the reset line 13, the image/character converter 16 itself is reset. Furthermore, when a reset signal is applied from the reset line I3, the image signal and character signal stored in the built-in memory are cleared. Output circuit 1
8 converts the character signal into an appropriate output format suitable for external equipment and outputs it, and outputs a reset signal to the reset line 13 when the output is completed. The reset signal on the reset line 13 is further applied to the first, second, and third self-holding circuits 7 to 17, respectively, to set the self-holding to a reset state. Note that the constant value stored in the constant circuit 14 in advance is larger than the count value obtained from the wide space and wide bar when the photoelectric converter 1 is scanned over the bar code at a normal speed, and It is set to a value with a margin that fully takes into account changes in speed. Furthermore, the bit/image conversion circuit 11 and the image/image conversion circuit 11
Character conversion circuit! 6 and output circuit 18 form the decoding means.

A configuration having such a start determination processing procedure is 1ci
It is explained using Table 2 in [Manufacturing of barcode system] described on pages 438 to 451 of the magazine Transistor Technology published by CQ Publishing on April 1, 1984, and some additions and modifications have been made to this. The contents were described on pages 179 to 199 of the separate magazine transistor technology editorial department published by CQ Publishing on July 1, 1984 [Production of barcode system]
An explanation using Table 2 is disclosed.

In such a configuration, as shown in FIG. 4 (1) (a),
If a sufficient start margin is provided in front of the bar code and photoelectric converter 1 is scanned over the bar code from a starting position sufficiently distant from the bar code, then A binary signal as shown in FIG. 4(2) is output. Then, the edge (2) falling from "H" to "L" is detected by the falling detection circuit 5, and the counting circuit 6 starts counting.Next, at the first bar, the edge "2" falls from "L" to "H".
The count value t1 until the rising edge ■ is detected by the edge detection circuit 4 is larger than the constant value, and the count value becomes ≧ the constant value before the photoelectric converter 1 reaches the first bar.
A signal is output from the comparator circuit 12, and the third self-holding circuit 1
7 is set and the second switch 8 is opened.

Therefore, even if an edge detection signal is output from the edge detection circuit 4 at the edge (2), it is not applied to the reset line 13 as a reset signal. Then, the counting circuit 6 starts counting by the edge detection signal at this edge ■.
The second self-holding circuit 10 is placed in the set state, the third switch 9 is closed, and the bit image conversion circuit 11 is counted by the counting circuit 6 between one edge and the next edge by the subsequent edge detection signal. Read count values sequentially. As a result, an appropriate start determination can be made. When the scanning on the bar code is completed, the binary signal of the binary conversion circuit 2 stops changing, the edge detection circuit 4 does not output an edge detection signal, and the count value of the counting circuit 6 increases. When the value is greater than or equal to the constant value, a signal is output from the comparator circuit 12.

Here, the fourth switch 15 is closed, and the signal from the comparison circuit 12 is applied as a decode signal to the image/character conversion circuit 16 to make a stop determination.

(Problem to be solved by the invention) However, the throat, bar and
If there is dirt D in front of the code, a proper start determination cannot be made even if the photoelectric converter 1 is scanned over the bar code from a starting position sufficiently distant from the bar code.

By scanning the photoelectric converter 1 as shown in FIG. 4(1)(b), a binary signal as shown in FIG. 4(3) is outputted from the binarizing circuit 2. Then, the edge ω' falls in the falling detection circuit 5.
is detected, the counting circuit 6 starts counting, and the count value tbI until the next edge (2) is detected by the edge detection circuit 4 is smaller than the constant value. Therefore, the comparison circuit 12
No signal is output from the third self-holding circuit 1 yet.
7 remains in the reset state and the second switch 8 remains closed. Therefore, the edge detection signal outputted from the edge verification circuit 4 at the edge ■' is applied as a reset signal to the reset line 13 via the second switch 8, stopping the counting of the counting circuit 6, and 2 self-holding circuit 7. IO is reset. However, Etsuji■
The count value between ' and the next edge ■' is not read into the bit image conversion circuit 11. Furthermore, the edge ■' is detected by the falling detection circuit 5 and the counting circuit 6 starts counting, but if the count value tb2 until the next edge Φ' is detected by the edge detection circuit 4 is smaller than the constant value. For example, similarly to the above, the edge detection signal of edge ■' is applied to the reset line 13 as a reset signal, and the count value between this edge ■' and the next edge ■' is
It is not read into the bit image conversion circuit 11. In this way, if there is dirt D or the like in front of the bar code, a sufficient start margin will not be provided, and proper start determination will not be possible.

Furthermore, as shown in FIG. 4(1)(C), even if the photoelectric converter 1 scans the bar code from a starting position close to the bar code, a proper start determination cannot be made. this is,
By scanning the photoelectric converter 1 as shown in FIG. 4(1) (C), a binary signal as shown in FIG. 4(4) is output from the binarizing circuit 2. Then, the count value tc counted between the edge ■'' and the next edge ■'' is smaller than the constant value, and the start determination cannot be made in the same way as above.

By the way, if the bar code surface is dirty, the widths of bars and spaces will be detected incorrectly, making it impossible to read the bar code properly. Therefore, the optical reading device of the conventional bar code reader assumes that if there is no dirt D in the space of a predetermined width provided immediately in front of the bar code, the bar code surface is also free of dirt. For this purpose, a start margin is provided immediately before the bar code, and the photoelectric converter 1 is configured to scan this start margin. As this start margin, a space with a width more than 10 times the narrow bar is provided.

Therefore, the optical reading device of the conventional bar code reader has a problem in that the bar codes cannot be arranged densely enough to provide a sufficiently wide star margin.

In addition, as another conventional example of an optical reading device for a bar code reader, there is a value corresponding to the time from the fall of the binary signal due to the start of scanning of the photoelectric converter 1 to the rise due to the first bar, and Some methods determine the start by comparing the width of the bar with the product of a constant value multiplied by a value corresponding to the elapsed time. space is still required.

An object of the present invention is to solve the problems of the optical reading device of the conventional bar code reader described above. An object of the present invention is to provide an optical reading device for a code reader.

(Means for solving the problem) In order to achieve this purpose, the bar code of the present invention
The optical reading device of the reader includes a detection means that outputs a read signal according to a code displayed on the medium, an edge detection means that detects an edge of the read signal, and a count for each edge detected by the edge detection means. a counting means for starting counting, and a count value started by this counting means that is a quotient of the maximum allowable width of the code divided by the minimum allowable width and the count value counted between the immediately preceding edges by the counting means. or the quotient obtained by dividing the count value started by the counting means by the count value counted between the immediately preceding edges is the height of the maximum allowable width of the code divided by the minimum allowable width. or the quotient obtained by dividing the count value started by the counting means by the quotient of the maximum allowable width of the code divided by the minimum allowable width is greater than or equal to the count value counted between the previous edges. and determining means for outputting a reset signal to the decoding means for reading and decoding the count value when .

(Function) Therefore, based on the numerical relationship between the count value at which counting was started by the counting means and the count value counted between edges according to the width of the immediately preceding code, a reset signal is given to the decoding means to start a new count. To read a value into a decoding means or to continue reading a count value without giving a reset signal to the decoding means.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block circuit diagram of an optical reading device for a bar code reader of the present invention, and FIG. 2 is a diagram illustrating the operation of the device of FIG. 1. In FIG. 1, circuit blocks that are the same as those in FIG. 3 are given the same reference numerals and redundant explanations will be omitted.

In FIG. 1, a binary signal outputted from a z-value conversion circuit 2 is applied to an edge detection circuit 4 via a normally open first switch 3, and is also applied to a space bar edge detection circuit 20. This space/bar/edge detection circuit 20 detects the edge that is switched from "L" to "H" output from the binarization circuit 2 when the photoelectric converter 1 goes from a space to a bar, and generates a short pulse-like edge. An edge detection signal is output. This edge detection signal is applied to the counting circuit 6 to reset it and start counting, and is also applied to the self-holding circuit 7 to set the self-holding. This self-holding Depending on the set state of the circuit 7, the first switch 3 is closed with a slight delay from the edge detection signal.By closing the first switch 3, the star/edge detection circuit 4 detects the "H" level of the subsequent binary signal. to “L”, and “
It detects any edge that switches from "L" to "H" and outputs a short pulse-like edge detection signal.This edge detection signal is applied to the counting circuit 6 to reset it and start counting. , is also given to an edge counting circuit 21, a memory circuit 22 serving as a memory means, and a bit image converting circuit 11. is given to the second comparison circuits 24 and 25. The multiplication circuit 23 multiplies the count value by a constant value, for example, a constant 8, which is larger than the quotient of the maximum allowable width of the wide bar divided by the minimum allowable width of the narrow space, and The product is output to the switching circuit 26.The switching circuit 26 receives the product from the multiplier circuit 23, and also receives the product from the first constant circuit 27.
The first constant value is given by , and the product is usually selected, but
The first constant value is selected only when a reset signal is applied from the reset line 13. Note that this first constant value is
It is set in advance to be greater than the maximum count value of the counting circuit 6. The value selected by the switching circuit 26 is given to the memory circuit 22, and each time the edge detection signal from the edge detection circuit 4 and the reset signal from the reset line 13 are given, the stored value is updated and the value is sent to the first comparison circuit. Output to 24. The first comparison circuit 24 compares the new count value whose counting has been started by the counting circuit 6 with the stored value, and outputs a signal when the new count value≧the stored value. This signal is applied as a reset signal to the image/character conversion circuit 16 and the reset line 13 via the normally closed second switch 28. When the edge counting circuit 21 counts, for example, three edge detection signals from the edge detection circuit 4, it enters the set state, opens the second switch 28, closes the normally open third switch 29, and connects the reset line 13 to the set state. It is reset by the reset signal. Second comparison circuit 25
compares the second constant value from the second constant circuit 30 with the count value, and outputs a signal when the count value≧the second constant value. This signal is sent to the image via the third switch 29.
It is given to the character conversion circuit 16 as a decode signal. The second constant value is larger than the count value obtained from the wide bar when the photoelectric converter 1 scans the bar code at a normal speed, and also takes into account changes in the scanning speed of the photoelectric converter 1. It is preset to a value with some margin.

Furthermore, a determining means is formed including the memory circuit 22, the multiplication circuit 23, and the first comparison circuit 24.

In such a configuration, as shown in FIG. 2 (1) (a),
If a sufficient start margin is provided just before the bar code, and the photoelectric converter 1 is scanned over the bar code from a sufficiently distant start position, then the binarization circuit 2 will be able to scan the bar code as shown in FIG. A binary signal as shown in 2) is output.

Then, the space bar edge detection circuit 20 detects the edge (2) rising from "L" to "H" due to the first bar, and the counting circuit 6 starts counting. The count value tal until the edge (2) which changes from "H" to "L" at the end of this first bar and transitions to a space is detected by the edge detection circuit 4 is smaller than the first constant value and the first comparison circuit 24 No signal is output from .Then, at edge ■, the product of this count value 〇 multiplied by constant 8 is stored in memory circuit 2.
2. Next, the space between the edge ■ and the next edge ■ is counted, and a new count value t42 due to this space and 8×t stored in the memory circuit 22 are counted.
aI is compared in the first comparison circuit 24, but if it is a normal bar code, tax<8Xta+, and the first comparison circuit 24 does not output a signal. In this way, it is determined that the start has been properly performed. Furthermore, when the edge detection circuit 4 outputs three edge detection signals, the second switch 28 is opened and the third switch 29 is closed, and thereafter a stop determination is made. This stop judgment is made when the scanning on the bar code is completed, the edge is no longer detected due to the stop margin provided immediately after the last bar, and the count value of the counting circuit 6 increases, and the count value of the second constant circuit 30 increases. When it becomes larger than the second constant value, the second comparison circuit 25 provides a decode signal to the image/character conversion circuit 16 . Then, a character signal is output based on this decoded signal, and further converted into an appropriate output format by the output circuit 18 and output. When the output by the output circuit 18 is completed, a reset signal is output to the reset line 13 and the initial state is restored.

Further, if there is dirt D in front of the bar code as shown in FIG. 2(1)(b), a binary signal as shown in FIG. 2(3) is output. Then, due to the dirt D, the binary signal rises from "L" to "H", and the edge
The edge detection circuit 20 detects this, and the counting circuit 6 starts counting. The count value tbj until the edge ■', which changes from "H" to "L" after the dirt D disappears, is detected by the edge detection circuit 4 is smaller than the first constant value and is the first constant value.
No signal is output from the comparison time W¥24. Then, at edge ■', the product obtained by multiplying this count value tbl by a constant 8 is stored in the storage circuit 22. Next, if the space from the stain D to the first bar is wide and the count value tb2 is large and tb2≧8Xtb, the first comparison circuit 24
A reset signal is output to the reset line 13, and the image/character conversion circuit 16 is cleared to return to its initial state. Furthermore, the edge ■' of the first bar is detected by the space bar edge detection circuit 20, and the counting circuit 6 starts counting, and the same operation as when there is no dirt D is performed, and the edge ■' and the next edge The product obtained by multiplying the count value tb3 between edge ■' and the next edge ■' by a constant 8 is compared with the count value tb4 between edge ■' and the next edge ■'. It will be judged. Note that the above constant was explained as "8" for binary level bar code display, but it can also be used for multilevel bar code display (3 to n values), for example, for wide bar. It is sufficient to appropriately select and set a value based on the maximum allowable width and the minimum allowable narrow space width.

In this way, the stain D is determined by multiplying the count value tbl obtained from the width of the stain D by a constant, and the new count value tb obtained from the width of the space that follows.
2, the smaller the width of the stain D is, the wider the space is relatively, so it can be determined to be the stain D with certainty. This means that while any contamination can be easily noticed and removed by visual inspection of the bar code, the width of the bar prevents fine contamination from being read as a bar unnoticed and increases the reliability of bar code reading. It can improve sex.

In addition to the general display environment such as dirt, etc., the scan start position is marked on the front surface to be scanned with a line with high light absorption rate, such as a square frame (for example, the weekly magazine "Weekly" published by Tokyo News Tsushinsha Co., Ltd.). TV Guide September 19th issue” (1986/9/
19 (Issue)) is displayed on page 100), if there is a light reflecting part after this frame that is at least larger than the product of the width of the frame and the constant, the above-mentioned Similar to stains, etc., the frame is determined to be not part of the bar code.

Furthermore, as shown in FIG. 2(1)(c), when the photoelectric converter 1 is scanned from a starting position close to the bar code,
A binary signal as shown in FIG. 2 (4) is output. Then, the edge ■'' is detected by the space bar edge detection circuit 20, and the edge ■'' and the next edge ■'' are sequentially detected by the edge detection circuit 4, and between that edge ■'' and the next edge ■'' Figure 2 (2)
Similarly to the binary signal, an appropriate start determination is made.

In the above embodiment, "L" is output with the space being white, and "H" is output with the bar being black, but the present invention is not limited to this. And the space bar
The edge detection circuit 20 may be of any type as long as it detects an edge transitioning from a space to a bar and outputs an edge detection pulse.

Further, in the above embodiment, the product of the count value counted between the immediately preceding edges by the counting circuit 6 and a constant is stored in the storage circuit z2 as a start determination, and this stored product is applied to the first comparison circuit 24. However, the counting circuit 6
The count value counted between the immediately preceding edges may be stored in a storage circuit, and the product obtained by multiplying this immediately preceding count value by a constant in a multiplication circuit may be provided to the first comparator circuit 24.

In the above embodiment, when the count value at which the counting circuit 6 has started counting is on the product of the count value counted between the immediately preceding edges and the constant, the first comparator circuit 24 outputs a reset signal. However, when the quotient obtained by dividing the count value at which the counting circuit 6 started counting by the count value counted between the immediately preceding edges becomes greater than a constant, or when the counting circuit 6 starts counting. The decoder may be configured to output a reset signal to the decoding means when the quotient obtained by dividing the counted value by a constant becomes equal to or greater than the count value counted between the immediately preceding edges.

Furthermore, although the above embodiments have been described with reference to bar code display, if - several characters, marks, etc. are displayed in accordance with the minimum width and maximum width regulations, then the count value that is started by the counting means Based on the numerical relationship between this and the count value counted between edges according to the width of the immediately preceding code, it is possible to make a start determination and reset the decoding means or not to reset it, thereby improving the decoding probability.

Further, even in a device in which all the count values of the counting circuit 6 are temporarily stored in a storage device and the count values are read out later and the start determination process is performed, the decoding probability can be similarly improved. Here, when determining the start of characters, etc., the determination is made based on a constant determined based on the maximum permissible display width of the character and the minimum permissible width of the display interval of this character. It is desirable that the process performs the start determination after the data is once edited as one character's worth of data.

(Effects of the Invention) As explained above, according to the optical reading device of the present invention,
The start is judged based on the numerical relationship between the count value at which counting was started by the counting means and the count value counted between edges according to the width of the immediately preceding code, and if it is incorrect, a reset signal is sent to the decoding means. Therefore, if a count value corresponding to an incorrect code is read into the decoding means, it is immediately reset and a new count value is read, and the probability of decoding the information read into the decoding means is high. Further, the determination as to whether the start is proper or improper is not affected by the scanning speed at which the code is read by the detection means, and is determined at a time corresponding to the scanning speed. Furthermore, the space provided in front of the displayed code is narrower than in conventional devices of this type, which reduces the occurrence of reading errors due to dirt, etc., and makes it easier to read codes displayed in high density. It has the excellent effect of being possible.

[Brief explanation of the drawing]

FIG. 1 is a block circuit diagram of an optical reading device for a bar code reader according to the present invention, FIG. 2 is a diagram explaining the operation of the device in FIG. 1, and FIG. 4 is a block circuit diagram of an optical reading device of a bar code reader, and FIG. 4 is a diagram explaining the operation of the device of FIG. 3. FIG. 2: Binarization circuit, 4: Edge detection circuit, 6: Counting circuit, 11: Bit/image conversion circuit, 16: Image/character conversion circuit, 18: Output circuit, 22: Memory circuit, 23: Multiplication circuit, 24 :First comparison circuit. Patent applicant Alps Electric Co., Ltd.

Claims (2)

[Claims] (1) A detection means that outputs a read signal according to a code displayed on the medium, an edge detection means that detects an edge of the read signal, and a counter that starts counting for each edge detected by the edge detection means. means, and the count value started by the counting means is greater than or equal to the product of the quotient of the maximum allowable width of the code divided by the minimum allowable width and the count value counted between the immediately preceding edges by the counting means. or when the quotient obtained by dividing the count value started by the counting means by the count value counted between the immediately preceding edges is greater than or equal to the quotient obtained by dividing the maximum allowable width of the code by the minimum allowable width, or when the quotient obtained by dividing the count value started by the counting means by the quotient of the maximum allowable width of the code divided by the minimum allowable width is greater than or equal to the count value counted between the immediately preceding edges; 1. An optical reading device comprising: determination means for outputting a reset signal to decoding means for reading and decoding count values. (2) The determination means includes a multiplication means for multiplying the count value counted by the counting means by a constant value greater than or equal to the quotient of the maximum allowable width of the code divided by the minimum allowable width, and an output from the multiplication means. Claim 1, characterized in that it has a storage means for storing the product obtained by the counting means, and a comparison means for comparing the stored value stored in the storage means with the count value at which counting is started by the counting means. The optical reader described.