JPH0570192B2 - - Google Patents

Description

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

(b) Conventional technology A barcode reader projects a laser beam onto a barcode label, converts the scattered reflected light from the barcode label into an electrical signal using a receiver, and processes the electrical signal using a microcomputer. This is a device that decodes barcodes.

(c) Problems to be solved by the invention Bars used in barcodes have a width of 1 mm.
There is a thick bar with a width of 0.2 mm and a thin bar with a width of 0.2 mm. Since a barcode reader capable of reading both barcodes using thick bars and barcodes using thin bars has not been realized, dedicated barcode readers are required for each. For this reason, for example, if a barcode label using a thick bar and a barcode label using a thin bar are flowing together on a belt conveyor, one for a thick bar and another for a thin bar may flow together. It was necessary to install two types of barcode readers for the bar. For this reason, equipment costs have increased and installation space has also increased.

The reason why one type of barcode reader could not read both thick bar and thin bar codes is as follows. In other words, since a barcode reader for thick bars uses a laser beam with a large diameter, when this beam is applied to a barcode using thin bars, the laser beam will be irradiated across two or more bars. This causes the analog electrical signal obtained by the photoreceiver to have very poor sensitivity, making it impossible to read barcodes.

The present invention aims to solve the above-mentioned problems and provide a barcode reader capable of reading both thick bar and thin bar codes.

(d) Means for Solving the Problems The present invention switches the cutoff frequency of an analog electrical signal to one for a thick bar and one for a thin bar, and also determines whether it is for a thick bar or a thin bar.
The above problem is solved by employing only data that has undergone appropriate blocking processing. That is, the present invention scans one barcode multiple times using a light beam with a beam diameter that allows the narrow bars to be identified, and scans a predetermined number of analog electrical signals obtained thereby. For the remaining analog electrical signals, frequencies higher than the first cutoff frequency are cut off, frequencies higher than the second cutoff frequency higher than the first cutoff frequency are cut off, and frequencies higher than the first cutoff frequency or the second cutoff frequency are cut off. bar width data is obtained from the analog electrical signal that is interrupted, the data thus obtained is stored for multiple scans, the bar width distribution for each scan is obtained, and the bar code is read from the bar width distribution. It is determined whether the bar is a thick bar or a thin bar, and if it is determined that the bar is a thick bar, if it is data in which frequencies higher than the first cutoff frequency are cut off, this is adopted, and the second
If it is data in which a frequency higher than the cutoff frequency is cut off, cancel it, and if it is determined to be a thin bar, if it is data in which a frequency higher than the second cutoff frequency is cut off, it is adopted, If the data is cut off at a frequency equal to or higher than the first cutoff frequency, it is canceled and the thus adopted data is decoded.

Further, the signal processing device of the barcode reader that implements the method of the present invention includes a cut-off frequency switching amplifier 24 that cuts off a portion of an analog electrical signal having a predetermined frequency or higher and is capable of switching the predetermined frequency; A binarization circuit 26 that converts the analog electrical signal from the bar into a binary signal, and a bar width digitization circuit 28 that calculates the bar width from the binary signal.
A storage device 32 that stores data from the bar width digitization circuit 28 and a cutoff frequency of the cutoff frequency switching amplifier 24 are alternately set between the first cutoff frequency and a second cutoff frequency higher than the first cutoff frequency or every predetermined number of times. A switching command means for switching, a distribution calculation means for calculating the bar width distribution of the data of one scan stored in the storage means, and a distribution result obtained by the distribution calculation means that the bar code uses thick bars. A bar determination means determines whether the data is a thick bar or a thin bar, and if the bar determination means determines that the bar is a thick bar, it determines whether this data was cut off at the first cutoff frequency or the second cutoff frequency. thick bar selection means for determining the data, and employing this data when the data is cut off at the first cutoff frequency, and canceling this data when the data is cut off at the second cutoff frequency; and bar determination means. If it is determined that the bar is a narrow bar, it is determined whether this data is cut off at the first cutoff frequency or the second cutoff frequency, and if it is cut off at the second cutoff frequency, this data is adopted. At the same time, when the data is cut off at the first cutoff frequency, the narrow bar sorting means cancels the data, and the data adopted by the thick bar sorting means or the narrow bar sorting means decodes the data and converts it into a predetermined code. and a decoding means for converting into.

(E) Effect The first cutoff frequency is suitable for a thick bar, and the cutoff frequency is set to a relatively low value. Therefore, signals with a higher frequency than the frequency corresponding to the thick bar are blocked. On the other hand, the second cutoff frequency is adapted to the thin bar, and the cutoff frequency is set to a higher frequency than the frequency corresponding to the thin bar. Therefore, when processing at the first cutoff frequency, a normal output is obtained when the barcode uses thick bars, but on the other hand, when the barcode uses thin bars, the signal is completely cut off. This results in a state where there is no output. Furthermore, when processing is performed at the second cutoff frequency, a normal output is obtained when the barcode is a thin bar, but on the other hand, when the barcode is a thick bar, noise is included.

Therefore, if it can be determined whether the analog electrical signal is a scanned barcode using thick bars or a barcode scanned using thin bars, normal outputs corresponding to the thick bars and thin bars are selected. be able to. In other words, if it is determined that the barcode uses thick bars, data processed at the first cutoff frequency may be adopted, and if it is determined that the barcode uses thin bars. In this case, data processed at the second cutoff frequency may be used. Whether the scanned barcode is a barcode using thin bars or a barcode using thick bars can be determined from the bar width distribution. In other words, there are two types of bar width: wide and narrow, and if we take the distribution of bar width during one scan, it will basically be distributed into two types: wide bar and narrow bar. Become. Even when noise is included, these distributions are small, so it can be determined from the distribution of bar widths whether the analog electrical signal is one obtained by scanning a thick bar or one obtained by scanning a thin bar. This results in
Only normal data can be extracted. Therefore, it is possible to read both thin bar and thick bar codes using one type of bar code reader.

(F) Embodiment FIG. 1 shows a block diagram of the optical system and signal processing section of a barcode reader. The projector 10 can project a laser beam onto the polygon mirror 14 in response to a command signal from the laser drive unit 12. Note that the laser beam diameter is set to be relatively small so that a narrow bar can be detected. The polygon mirror 14 is rotationally driven by a polygon mirror drive section 16. By rotating the polygon mirror 14, the laser beam scans over the barcode 18 printed on the barcode label. The reflected light from the barcode 18 is transmitted to a light receiver 2 composed of a photodiode.
0 is received and converted into an electrical signal. The analog electrical signal from the photodetector 20 is input to a current-voltage conversion amplifier 22, and the analog electrical signal converted and amplified by the current-voltage conversion amplifier 22 is input to a cutoff frequency switching amplifier 24. The cutoff frequency switching amplifier 24 has a function of cutting off high frequency components of input analog electrical signals having a predetermined cutoff frequency or higher. The cutoff frequency of the cutoff frequency switching amplifier 24 can be switched by a command from a CPU (central processing unit) 27. Cutoff frequency switching amplifier 2
The signal processed in step 4 is converted to 2 in the binarization circuit 26.
It is converted into a value, and then converted into a numerical value indicating the bar width in the bar width digitization circuit 28.
The signals from the DMA circuit 30 can be stored in a RAM (memory device) 32 by the DMA circuit 30. CPU27 is RAM3
2 and ROM 34 can be accessed.

The apparatus shown in FIG. 1 performs the following operations. First, the barcode 18 is scanned. That is, a laser beam is projected onto the barcode 18 by the action of the polygon mirror 14, and the barcode 18 is scanned. Scanning by laser beam is one barcode 18
It is performed 30 times for The analog electrical signal obtained by the photoreceiver 20 is converted into a current-voltage conversion amplifier 2.
2 is converted and amplified into an analog electrical signal, and then converted into a numerical value indicating the bar width by a binarization circuit 26 and a bar width digitization circuit 28, and is stored in the RAM 32. However, a predetermined high frequency component of the analog voltage signal is cut off in the cutoff frequency switching amplifier 24. The cutoff frequency is switched between a first cutoff frequency and a second cutoff frequency for each scan. Therefore, 15 scans are cut off at the first cutoff frequency, and the remaining 15 scans are cut off at the second cutoff frequency. The first cutoff frequency is set to a relatively low value so as to be appropriate for the thick bar. On the other hand, the second
The cutoff frequency is set to a relatively high value to be suitable for thin bars. Therefore, when the barcode 18 uses a thick bar, the analog signal when processed at the first cutoff frequency becomes normal as shown in FIG. 2a, and when processed at the second cutoff frequency As shown in FIG. 2b, chips, stains, etc. in bar printing are detected, resulting in an analog signal containing noise. On the other hand, when scanning the barcode 18 using a thin bar, when processed at the first cutoff frequency, the frequency of the signal obtained by the bar falls into the cutoff region, so there is no output as shown in Figure 3a. When processing is performed at the second cutoff frequency, a normal output as shown in FIG. 3b is obtained.

The data of 30 scans stored in the RAM 32 is processed by the CPU 27 as follows. That is, first, the bar width distribution of the first data is determined. Since the bar width consists of two types, narrow bar and wide bar, when a normal output signal is obtained as in the case of Figure 2 a and Figure 3 b mentioned above, the bar width distribution As shown in FIG. 4, this concentration is concentrated at two points in the width dimension of the narrow bar and the wide bar. Therefore, it is possible to determine whether the bar is a thick bar or a thin bar.
In the case of Fig. 2b mentioned above, since noise is included, the distribution as shown in Fig. 5 occurs in locations other than the width dimensions of the narrow bar and wide bar, but the narrow bar and wide bar serving as the reference. Since the number of bars distributed in the width dimension is large, it is possible to judge whether the bar is a thick bar or a thin bar based on the part with the largest distribution. Note that in the case of FIG. 3a described above, the output signal is 0, so the process of determining whether a thick bar or a thin bar is based on the distribution is actually meaningless. After determining whether the bar is a thick bar or a thin bar as described above, if the bar is determined to be a thick bar, if the current data is processed at the first cutoff frequency, it is adopted as data. However, those processed at the second cutoff frequency are canceled. On the other hand, if it is determined that the bar is a narrow bar, data processed at the second cutoff frequency is adopted, and data processed at the first cutoff frequency is canceled. The above process
After doing this on 30 pieces of data, the obtained 15
A decoding program is executed using the data for each batch, and the decoding results obtained are converted into a predetermined code and output. The above process is shown in a flowchart as shown in FIG.

After all, as a result of the above operation, if the barcode 18 uses thick bars, the barcode is decoded only from the data processed at the first cutoff frequency for the thick bars. Furthermore, if the barcode 18 uses a thin bar, the barcode is decoded only from the data processed at the second cutoff frequency for the thin bar, and any barcode 18 can be read. be.

In this embodiment, the cutoff frequency is switched every scan, but the cutoff frequency may be switched every multiple times, or between the first half and the second half of the scan. In addition, the number of scans is
Although the number of times is 30, it goes without saying that the number of times other than this may be used, and the processing using the first cutoff frequency and the processing using the second cutoff frequency do not necessarily have to be performed the same number of times. Furthermore, the decoding program does not necessarily need to use all of the data from 15 times, for example, and may output the results if the decoding results of the first two data of the 15 times match. , or only the first data may be used. Therefore, even if a barcode passes through before completing all 30 scans (for example, data for only 10 scans can be obtained), the operation of the above embodiment will still work. Can be read.

(G) Effects of the Invention As explained above, according to the present invention, it is possible to determine whether a read barcode is a thin bar code or a thick bar code, and to set an appropriate cutoff frequency in each case. Since processed data is used, it is possible to read both thick bar and thin bar codes with one bar code reader.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a diagram showing an analog signal in the case of a thick bar, FIG. 3 is a diagram showing an analog signal in the case of a thin bar, and FIG. 4 is a diagram showing an analog signal in the case of a thin bar. Figure 5 is a diagram showing the bar width distribution in the case of a normal signal, Figure 5 is a diagram showing the bar width distribution in a state where noise is included, Figure 6 is a diagram showing the control flow, and Figure 7 is a diagram showing the present invention. FIG. 2 is a diagram showing the relationship between components of the signal processing device of FIG. 18... Bar code, 24... Cutoff frequency switching amplifier, 26... Binarization circuit, 27... CPU, 28... Bar width digitization circuit, 32... RAM (storage device).

Claims (1)

[Claims] 1. In a signal processing method 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 light beam has a beam diameter that allows narrow bars to be identified. One barcode is scanned multiple times using As for the signal, a frequency equal to or higher than a second cutoff frequency, which is higher than the first cutoff frequency, is cut off, and bar width data is obtained from the analog electrical signal in which frequencies equal to or higher than the first cutoff frequency or the second cutoff frequency are cut off. data for multiple scans,
Next, the bar width distribution for each scan is determined, and it is determined from the bar width distribution whether the read barcode is a thick bar or a thin bar. If it is determined that the bar code is a thick bar, the first cutoff frequency is determined. If the data cuts off a frequency higher than or equal to the second cutoff frequency, it is adopted; if the data cuts off a frequency higher than or equal to the second cutoff frequency, it is canceled; and if it is determined that the bar is narrow, the second cutoff frequency is used. If the data has a frequency higher than the first cutoff frequency cut off, it is adopted, and if the data has a frequency higher than the first cutoff frequency cut off, it is canceled, and the thus adopted data is decoded. Features of barcode reader signal processing method. 2 Barcode 1 is generated from an analog electrical signal obtained by photoelectrically converting the optical signal obtained by scanning the barcode 18.
A signal processing device for a barcode reader that decodes a barcode reader 8 includes a cutoff frequency switching amplifier 24 that cuts off a portion of an analog electrical signal having a predetermined frequency or higher and can switch the predetermined frequency, and an analog electrical signal from the cutoff frequency switching amplifier 24. A binarization circuit 28 that converts a signal into a binary signal, a bar width digitization circuit 28 that calculates a bar width from the binary signal, and a bar width digitization circuit 2
8, and a switching command means for switching the cutoff frequency of the cutoff frequency switching amplifier 24 between the first cutoff frequency and a higher second cutoff frequency alternately or every predetermined number of times. , a distribution calculation means for calculating the bar width distribution of the data of one scan stored in the storage means, and a distribution result obtained by the distribution calculation means to determine whether the barcode uses thick bars or thin bars. bar determining means for determining whether the bar is a thick bar; Thick bar selection means employs this data when the bar is cut off at the cutoff frequency, and cancels this data when the bar is cut off at the second cutoff frequency, and the bar determination means determines that the bar is thin. In this case, it is determined whether this data was cut off at the first cutoff frequency or the second cutoff frequency, and if the data was cut off at the second cutoff frequency, this data is adopted and the first cutoff frequency is used.
When the data is cut off at the cutoff frequency, the narrow bar sorting means cancels this data, and the data adopted by the thick bar sorting means or the narrow bar sorting means decodes the data and converts it into a predetermined code. A signal processing device for a barcode reader, comprising: decoding means.