JPH02135581A - Signal processor for bar code reader - Google Patents

Abstract

PURPOSE:To make unnecessary the enlargement of a label dimension and to surely read a label even when the label is stuck in any direction by counting the number of times of switching between the binaries of binary signals, and accepting data when a counted value amounts to a reference value. CONSTITUTION:By being scanned by means of laser beams, reflected light from a bar code 18 is received by a light receiver 20, and an analog current signal is inputted to a current/voltage converting amplifier 22. The conversion- amplified analog voltage signal is binarized by a binarizing circuit 26, and by differentiating the binary signal by a differentiating circuit 36, a differentiating signal can be obtained. It is counted by a counter 38, a counting result is inputted to a CPU 27, and when the counted value is more than the reference value, the data based on the scanning at such a time are accepted. Thus, the length of a bar code may be short, and the restriction of the labeling direction and inclination is eased.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a signal processing device for a stationary barcode reader.

(b) Conventional technology Stationary barcode readers are used on assembly lines in factories, logistics lines for delivery, etc. A barcode reader reads barcodes on labels affixed to articles flowing on the conveyor. For this purpose, the barcode reader scans the barcode with a laser beam,
The barcode is decoded by photoelectrically converting the scattered reflected light using a light receiver and processing the resulting analog electrical signal.

(c) Problems to be solved by the invention However, in order to enable reading even when the line speed is high, in conventional barcode readers, label attachment is limited by the condition, label size, etc. There is a problem that there is.

That is, the label needs to be attached so that the barcode is tilted at an angle of ±5° or less with respect to the scanning direction of the laser beam. If the barcode has a large inclination, the effective area for reading the barcode in one direction (the area in which the laser beam can scan all the bars) becomes small. Also, when the first part of a tilted barcode is scanned, the read data (invalid data that does not scan all the bars) is processed, which takes time (decoding loss time). However, when the barcode is read again, the barcode has already passed and the barcode cannot be read. Therefore, as mentioned above,
The slope of the label must be within an acceptable range.

In addition, since the barcode has numbers and letters specified in JI 5X9001 (that can be read directly by humans), if these numbers and letters are located on the front side in the line running direction, Data processing is performed by reading these numbers and characters, and decoding loss time occurs as described above. This decoding loss time causes a problem that the barcode cannot be scanned again, or the area of the barcode that is effective for scanning becomes small and the reading rate decreases. In order to avoid this, it is necessary to attach the label so that the numbers and letters attached to the barcode are on the rear side in the direction of movement.

One way to solve the above-mentioned problems is to lengthen the barcode, that is, increase the size of the label in the running direction. However, in this case, the price of the label increases, and depending on the shape of the article, it may not be possible to attach a large-sized label. The present invention aims to solve these problems.

(D) Means for Solving the Problems The present invention solves the above problems by sorting data based on the number of times a binary signal switches between two values, and employing only data obtained by completely scanning a barcode. do. That is, the signal processing device for a barcode reader according to the present invention includes analog electricity, a binarization circuit that binarizes a signal, and a counter that counts the number of times the binary signal obtained by the binarization circuit switches between two values. and a comparison means that compares the counted value by the counter with a preset reference value, and when the comparing means determines that the counted value is smaller than the reference value, invalidates the data based on this scan and compares the counted value. and data selection means that employs data based on this scan when the comparison means determines that the reference value is greater than or equal to the reference value.

(e) If the operational barcode is tilted with respect to the scanning direction of the laser beam, only the bar at the top is scanned at the initial scanning stage. Therefore, the number of times the binary signal switches between two values is smaller than when all bars are scanned. In this case, since the number of times of switching between two values does not reach the reference value, the read data is canceled. When the laser beam passes through all the bars, the number of switching between the two values reaches a reference value. In this case, the read data is accepted as valid data.

Therefore, since only valid data can be obtained in the shortest possible time, the length of the barcode may be short, and restrictions on the direction and inclination of label attachment are relaxed. Note that the adopted data will be stored in, for example, a storage means and will be decoded. Therefore, the bar code is not decoded until valid data is manually input, and the bar code is decoded after valid data is manually input, so that reading is performed reliably without decoding loss time.

(f) Embodiment FIG. 2 shows an embodiment of the present invention as a block diagram. The projector 10 can project a laser beam according to a command from the laser drive section 12. The polygon mirror 14 is rotationally driven by a polygon mirror drive unit 16, and the light projector 10
A laser beam is reflected toward the barcode 18 and scanned. The reflected light from the barcode 18 of the label affixed to the article on the conveyor is received by the light receiver 20, and an analog current signal photoelectrically converted thereby is inputted to the current-voltage conversion amplifier 22. The analog voltage signal converted and amplified by the current-voltage conversion amplifier 22 is binarized by the binarization circuit 26, then converted into a numerical value indicating the bar width by the bar width digitization circuit 28, and this data is sent to the RAM 32 through the DMA circuit 30. be remembered. Furthermore, the binary signal from the binarization circuit 26 is transmitted to the differentiation circuit 3.
6, and a differential signal indicating the switching between two values of the binary signal obtained thereby is counted by a counter 38. The counting result of the counter 38 is input to the CPU 27 manually. The CPU 27 stores a predetermined program, etc.
OM34 is also connected.

Next, the operation performed by this embodiment will be explained. When the barcode 18 affixed to the article moving on the conveyor line reaches a predetermined position, it will be scanned by a laser beam. The reflected light from the barcode 18 is received by a light receiver 20, and an analog current signal is inputted to a current-voltage conversion amplifier 22.

The analog voltage signal converted and amplified by the current-voltage conversion amplifier 22 is binarized in a binarization circuit 26. As a result, when scanning the barcode 18 as shown in FIG. 3(a), a binary signal as shown in FIG. 3(b) is obtained. Next, the binary signal is passed through a differentiating circuit 36.
By differentiating at , a differential signal as shown in FIG. 3(C) is obtained. This differential signal indicates the number of times the binary signal switches between two values, and is counted by the counter 38. The counting results are input to the CPU 27. Note that the counter 38 receives a scan start pulse (Fig. 3(d)) which is a signal indicating that one scan is started in the optical system.
)) is reset by a reset signal (FIG. 3(e)) that is output when it is manually operated. Further, after outputting the differential signal and before the next scan is performed, data selection processing (FIG. 3(f)) is performed by the CPU 27 as described later.

The CPU 27 performs the following control.

First, the DMA circuit 30 specifies the address of the RAM 32 that stores the bar width numerical data (step 100 in FIG. 4). Next, a signal to reset the counter 38 is output at the same time as the scanning start pulse is input manually (10
2). Next, DMA activation for one scan is performed, and bar width numerical data for one scan is stored at a predetermined address in the RAM 32 (step 104). Next, the count value of the counter 38 is read (step 106), and the count value is compared with a reference value (step 108). The reference value is set in advance according to the standard of the barcode and the number of digits used. for example,
In the case of ITF standard, 4 each for start and stop.
Since there is switching between two values of , and there is switching between two values of 5 in one digit, a reference value of 8+5XN is selected for the number of digits N. If the count value is smaller than the reference value, the same address is held (step 110) and the operations from step 100 are repeated. On the other hand, if the count value reaches the reference value, it is determined whether or not the storage of data for 30 times into the RAM 32 has been completed (112), and if it has not been completed, the address is incremented (112). 114
) Return to step 100. When the storage of data for 30 times is completed, a program for decoding the bar width numerical data stored in the RAM 32 is executed (step 116).

By controlling as described above, the following effect can be obtained. For example, if the bar code moves in an inclined state with respect to the scanning direction of the laser beam as shown in FIG. 5, the bar width numerical data will not be decoded for the area A. This is because since the count value of the counter 38 is smaller than the reference value, the address is not incremented and the program does not proceed to the bar width numerical data decoding program. When scanning is applied to area B, the count value reaches the reference value, so 3
The bar width numerical data for 0 times is stored, and the process moves to a bar width numerical data decoding program. Therefore, even when the barcode 18 is tilted as shown in FIG. 5, the barcode can be decoded at the same time as scanning of area B is started. Conventionally, the bar width numerical data decoding program is also executed in area A, so the label may pass through the scanning position during the execution of this decoding program, or the scanning in area B may be repeated as many times as necessary. In some cases, the area C was covered before the image was read, making it unreadable. In the case of the present invention, since decoding is performed from the area B as described above, reading can be performed reliably. Also, even if the numbers and characters added to the barcode are scanned first, the program will not proceed to the bar width numerical data decoding program.
The label can be oriented in either direction.

(G) As described in detail, according to the present invention, the number of times a binary signal switches between two values is counted, and data when the counted value reaches a reference value is adopted. There is no need to increase the size of the label, the tolerance range for label inclination is increased, and the label can be reliably read no matter which direction it is attached.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the relationship between the constituent elements of the present invention, Fig. 2 is a block diagram showing an embodiment of the invention, Fig. 3 is a diagram showing the timing of each signal, and Fig. 4 is a control flow. Figure, 5th
The figure shows a state in which the barcode is tilted. 18...Barcode, 26...Binarization circuit, 27.
...CPU, 36... Differential circuit, 38... Counter. (a) 1-pull barcode (b) 1 (c) - and stop ■ - Binary signal differential signal (f) - conversion H data sorting process

Claims (1)

[Scope of Claims] 1. In a signal processing device for a barcode reader that decodes a barcode from an analog electrical signal obtained by photoelectrically converting an optical signal obtained by scanning a barcode, the signal processing device includes: a counter that counts the number of times the binary signal obtained by the binarization circuit switches between two values; a comparison means that compares the count value by the counter with a preset reference value; If the comparison means determines that the counted value is smaller than the reference value, the data based on this scan is invalidated, and if the comparison means determines that the counted value is greater than or equal to the reference value, the data based on this scan is adopted. A signal processing device for a barcode reader, comprising: data sorting means. 2. storage means for sequentially storing data adopted by the data selection means; and migration means for executing a data decoding program after data for a predetermined number of scans have been stored;
2. A signal processing device for a barcode reader according to claim 1. 3. As the reference value, a setting means is provided for setting the number of times the binary signal switches between two values, which should be obtained when a normal bar code is normally scanned, in accordance with the standard of the bar code and the number of digits of the bar code. 3. The signal processing device for a barcode reader according to claim 1, wherein