JP2733951B2 - Barcode reader - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bar code reader. In terms of current microprocessor technology, the invention is particularly effective when used in laser beam scanning bar code readers.

[Conventional technology]

Two types of bars that are optically different (white and black are common, and are simply referred to as white and black hereinafter) are alternately arranged, and the bar width is represented by a sign with information provided. The code is widely used in POS systems and the like. An apparatus for reading the barcode is a barcode reader, which is a first embodiment of the present invention, which shows a prior art of a hand-held laser beam scanning barcode reader that scans a barcode by scanning a laser beam. This will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a scanner which is held by a hand 2 and directed to a bar label 3 on which a bar code is described. A laser beam is emitted from a semiconductor laser 4 having a built-in scanner, and is optically oscillated right and left by a scanning mechanism 5 to form a bar label 3.
Is scanned. The scanning mechanism 5 is realized by, for example, a rotary polygon mirror. The intensity of the laser beam applied to the bar is modulated by the white / black of the bar and reflected, and the photoelectric conversion element 6
And converted into an electric signal here. Thereafter, the signal is converted into a binary signal indicating white / black by a binarization circuit 7, converted into data indicating a bar width by a bar width measurement circuit 8, and a bar decoding / editing / output unit 9 outputs a code indicating the bar. And output with a predetermined code. The above bar reading operation is started by the switch 10.

FIG. 2 shows the internal configuration of the bar width measuring circuit 8 according to the prior art. The change of the binary signal 35 indicating white / black (from white to black and from black to white) is detected by the edge detection circuit 31. The counter 32 counts the clock 34 after the edge detection circuit 31 detects the change, and the latch 33 holds the value of the counter 32 when the edge detection circuit 31 detects the change, thereby reducing the width of the bar. It is stored as a counter value. It is after the store operation by the latch 33 that the counter 32 is initialized and starts counting for the next bar.

In the prior art, the bar decode / edit / output unit 9 is realized by a microprocessor. The count value data 38 indicating the bar width measured by the circuit shown in FIG. 2 is read by an interrupt process in the microprocessor. The interrupt signal 36 is for indicating to the microprocessor that the latch 33 holds the count value, and the microprocessor reads the count value data 38 and the monochrome information 37 when the interrupt signal 36 is received. Count value data 38
Is obtained both for the white bar and the black bar, but the information indicating which bar the data was obtained is the black and white information 37.

The interrupt processing of the microprocessor could not catch up because of the extremely narrow bars, and if the count value data 38 was missed, the subsequent white and black writing positions would be reversed, making it impossible to read the barcode. Become. Even in such a case, in order to make it possible to distinguish between white and black and to read a barcode, it is an essential requirement to take in the black and white information 37 in addition to the count value data 38.

FIG. 3A shows a flowchart of the interrupt processing in the conventional microprocessor. Is processing for saving and restoring registers for interrupt processing. Is a process of reading the count value data 38 and writing it to the memory, and is a process of reading the black and white information 37 and writing it to the memory. FIG. 3B conceptually shows the contents written in the memory according to the flowchart of FIG. The black-and-white information 37 can be originally represented by one bit, but it is complicated (adjusting a program to be troublesome and processing time) to adjust a writing place in a bit unit in a normal microprocessor. Is the minimum unit for reading from and writing to memory).

[Problems to be solved by the invention]

In the case of a laser beam scanning bar code reader, to read a thin bar (interrupt signal is generated at short time intervals) written on a bar label at a position away from the scanner, it is necessary to correspond to a white bar or a black bar. FIG. 3 (a)
Has to be performed in about 25 μsec. On the other hand, it is difficult for a relatively inexpensive microprocessor to perform this processing in 25 μsec.

The present invention has been devised to solve this problem, and it is an object of the present invention to realize a device which can read even a thin bar by increasing a relatively small number of circuits despite slow interrupt processing.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a bar code reader for optically operating a code in which two types of optically different bars (hereinafter, each type is represented by a and b) are alternately described. A storage means for storing data representing the width of the bar a; a storage means for storing data representing the width of the bar b; a microprocessor having a bar decoding / editing / outputting function and having a memory; Interrupt instructing means for causing the microprocessor to start an interrupt process at the time of the change from a to b or the change from b to a by the scanning; and writing the data to the memory of the microprocessor. The positions at which they are inserted correspond to the storage means, respectively, and in the interrupt processing in the microprocessor, they correspond to the two storage means. And reading of data,
It is configured to perform the process of writing to the memory.

[Action]

Data corresponding to the bar widths a and b are stored in both storage units. At the point in time when the optical scanning changes from a to b or from b to a, the microprocessor performs interrupt processing by interrupt instructing means (an interrupt signal in the embodiment described later). In the interrupt process, the microprocessor performs a process of writing the data stored in both of the storage units into the memories provided for the respective storage units. As described above, at the time of the change from a to b or at the time of the change from b to a, the data stored in both storage means is fetched and written into the memory provided corresponding to each storage means. ,
b The two kinds of data are always taken as a set, and a,
are written in the order of b, a, b,... or in the order of b, a, b, a,. Therefore, a signal for discriminating between a and b (black and white information 37 in the related art) becomes unnecessary.

〔Example〕

FIG. 1 shows a bar code reader according to an embodiment of the present invention. The overall configuration is the same as that of the prior art described above.
Bar decoding, editing, and
The processing contents of the output unit 9 and the contents of data written to the memory of the microprocessor are different.

That is, the internal configuration of the bar width measuring circuit 8 in the case of the present invention is as shown in FIG. Edge detection circuit 3 in the figure
1, the binary signal 35 input to the counter 32 and the edge detection circuit 31 and the clock 34 input to the counter 32 are the same as in the case of FIG.
Changes from white to black and from black to white
Is a means for measuring the width of the white bar and the black bar as a count value. Reference numeral 51 denotes a black bar latch that holds the value of the counter 32 at the end of the black bar period.At the end of the white bar period, another black bar latch 52 holds the black bar latch 51 held by the black bar latch 51. The count value data is held, and the white bar latch 53 holds the white count value data output from the counter 32. Latch 52 for black bar and latch 53 for white bar
Are storage means for data representing the bar widths of black and white, respectively.

At the time when the data of one set of black and white bar widths is completed, that is, at the end of the period of the white bar (in other words, at the time when the binary signal 35 changes from white to black), the interrupt signal 54 informs the microprocessor. The interrupt processing for instructing the start of capture is started, and the microprocessor reads the black count value data 55 stored in the black bar latch 52 and the white count value data 56 stored in the white bar latch 53.

According to the interrupt instruction by the interrupt signal 54 described above,
Interrupt processing for reading the data 55 and 56 is executed. FIG. 5A shows a flowchart of the interrupt processing. Is a process required to start and end an interrupt, and performs a process of saving and returning a register, respectively. Is a process performed between the above and the above process, is a process of reading the black count value data 55 stored in the black bar latch 52 and writing it to the corresponding memory, and a process of storing the black count value data 55 in the white bar latch 53. This is a process of reading the written white count value data 56 and writing it in a memory corresponding to the data.

FIG. 5 (b) conceptually shows the contents written in the memory according to the flowchart of FIG. 5 (a), and corresponds to the data stored in the black bar latch 52 and the white bar latch 53. , The black count value data 1 and the white count value data 1 are written as a set, and then written in the same manner. As a result of being written in the memory in this manner, the count value data is always in the order of black / white / black / white. That is,
The position from the beginning to the odd number or the even number corresponds to the two storage means (the storage means for the black count value data and the storage means for the white count value data).

According to the present invention, when a very thin black line such as a boundary line between an article and a bar label is scanned, even if interrupt processing is not completed in time and data is lost, the count value data of the black bar and the white bar is always combined. Because it is imported, there is no mistake for black and white. That is, the black-and-white information 37 required in the related art is unnecessary.

In the embodiment shown in FIG. 4, the counter 32 is initialized when changing from white to black and from black to white, and the count value indicated by the counter 32 represents the width of the bar itself. However, the data representing the width of the bar captured by the microprocessor may not be the bar width itself. As another embodiment different from FIG. 4, the initialization is not performed when changing from white to black and from black to white, and the width of the bar is obtained by taking the difference between the values of the counters 32 that come after each other. It is also possible. That is, the counter
The initialization of 32 is performed only at the start of scanning by the scanning mechanism 5 (see FIG. 1), and thereafter, the clock 32 input to the counter 32 is counted, so that the counter 32 counts the accumulated elapsed time from the start of scanning. Measure time. Then, an embodiment is also possible in which the value of the counter 32 at the bar boundary is taken into the microprocessor and then the difference between the count values before and after the value is taken to determine the width of the bar.

In FIG. 4, latches 51 and 52 are black bar latches, and 53 is a white bar latch. When the binary signal 35 changes from white to black, an interrupt signal is given to the microprocessor. The embodiment in which black and white are reversed, and 51 and 52 are latches for a white bar and 53 is a latch for a black bar, and the microprocessor is interrupted at the time of change from black to white is also possible.

〔The invention's effect〕

 The present invention has the following effects.

(1) Improvement of Capturing Ability When comparing the flowchart of the prior art of FIG. 3 (a) with the flowchart of FIG. 5 (a), the processing of FIG. 3 (a) ends up reading one word. If the processing of FIG. 5A is also realized by the one-word reading processing, the interrupt processing time of both flowcharts is the same. That is, in the related art, only one bar width count value data can be read by the interrupt processing. However, the interrupt processing using the present invention can read two bar width count value data in the same processing time. In this case, if the same microprocessor is used, the reading process can be performed twice as fast as that of the conventional technology, so that the bar having a half width of the conventional bar can be read. Alternatively, if a bar of the same width is read, a microprocessor capable of processing at half the speed of the prior art can be used, which helps to reduce the cost of the apparatus.

(2) Reduction of Memory Used As can be seen by comparing FIG. 3 (b) and FIG. 5 (b),
When the bar width count value is fetched by using the present invention, it is not necessary to store the black and white information, so that the use effect of the memory is increased accordingly. If both the black and white information and the count value data occupy one word area, the present invention
With half the capacity, the same storage as before can be performed. In this way, the present invention can save the memory, which is useful for reducing the cost of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram of a laser scanning bar code reader according to an embodiment of the present invention, FIG. 2 is a bar width measuring circuit according to the prior art, and FIG. FIG. 4 (b) is an explanatory diagram of the contents stored in the memory, FIG. 4 (b) is a bar width measuring circuit according to an embodiment of the present invention, and FIG. FIG. 4B is a flowchart of an interrupt process of the microprocessor according to the embodiment of the present invention.
FIG. DESCRIPTION OF SYMBOLS 1 ... scanner, 2 ... hand, 3 ... bar label, 4 ... semiconductor laser, 5 ... scanning mechanism, 6 ... photoelectric conversion element, 7 ... binarization circuit, 8 ... bar width measurement circuit, 9: Bar decode / edit / output unit, 10: Push button switch, 31: Edge detection circuit, 32: Counter, 33: Latch, 34: Clock 35: Binarized signal, 36: Interrupt signal, 37: Black and white information, 38: Count value data, 51: Latch for black bar, 52: Latch for black bar, 53: Latch for white bar, 54: Interrupt signal, 55: Black Count value data, 56 ... White count value data.

Claims (1)

(57) [Claims] An optically different type (hereinafter, each type is referred to as a
And b) a bar code reading device that optically scans a code in which bars described alternately are read and stores data representing the width of the bar of a, and represents the width of the bar of b. A storage means for storing data; a microprocessor having bar decoding / editing / outputting functions and having a memory; and a time point of change from a to b or b to a by the above scanning.
Interrupt instruction means for causing the microprocessor to start interrupt processing at the time of the change to, the position at which the data is written to the memory of the microprocessor corresponds to the storage means, respectively, In the interrupt processing in the processor, reading of data corresponding to both of the storage means,
A bar code reader configured to perform the processing of writing to the memory.