JPH0320792B2 - - Google Patents

Description

[Detailed Description of the Invention] [Summary] This is a floating slice method for accurately extracting bar width information from barcode reading signals, which sequentially detects local maximums and minimums in the signal, and detects each adjacent maximum and minimum point. The slice level in between is set to the average value of the maximum and minimum values at each point.
These are executed by digital processing.

[Industrial application field]

The present invention relates to a floating slicing method for barcode reading signals in a barcode reading device.

[Conventional technology]

In conventional barcode reading devices, a barcode scanner such as a CCD sensor scans the barcode, and the resulting multi-valued barcode reading signal is sliced by an analog floating slicing circuit to correspond to the bar width. A binary signal is generated.

In an analog type floating slice circuit, the value of the internal time constant circuit is set so that the floating slice level follows the peak of the input signal at a level slightly lower than that.

FIG. 7 shows an example of generation of floating slice levels by such a conventional floating slice circuit. In the figure, v _i represents a barcode reading signal, and S _f represents a floating slice level.

Therefore, in a floating slice circuit, once the value of its time constant circuit is fixed, the floating slice characteristics are also automatically fixed, so it may not be possible to follow areas where there are sudden changes in bar width. The situation was ripe.

To explain using the example of FIG. 7, in the illustrated example, peaks P ₀ , P ₁ , P ₂ , and P ₃ correspond to the positions of the black bars,
A wide white bar exists between P ₀ and P ₁ . Therefore, the slice level S _f attenuates with a predetermined time constant between P ₀ and P ₁ and drops considerably at the position of P ₁ . Additionally, there is a narrow white bar between P ₁ and P ₂ , making the valley shallower. As a result, P ₁ ,
and P ₂ are sliced together and are perceived as one black bar, resulting in an error.

[Problem that the invention seeks to solve]

Conventional barcode reading devices use analog floating slice circuits, so they may not be able to track large changes in the barcode bar width, reducing reading accuracy and greatly impacting system reliability. There was a problem of giving

[Means for solving problems]

The present invention provides a floating slicing method that can always set an appropriate slice level by following a barcode reading signal without being affected by the magnitude of change in the bar width of a barcode.

Therefore, the present invention detects points having maximum and minimum values (hereinafter referred to as extreme points) from a barcode reading signal obtained by a barcode scanner, and sequentially calculates the values between two adjacent extreme points. The average value is calculated and used as the slice level between the two extreme points.

FIG. 1 is a diagram showing the basic configuration of the present invention.

In the figure, 12 is an A/D converter, which converts a barcode reading signal in a multi-value analog format obtained from a barcode scanner (not shown) into a digital signal.

Reference numeral 13 denotes an input data storage section, which stores the A/D converted barcode reading signal in time series.

Reference numeral 15 denotes a floating slice level generation unit, which sequentially reads barcode reading data stored in the input data storage unit 13 and detects local maximum values, local minimum values, and extreme value points that give the positions thereof. 151, and a slice level calculation unit 152 that sequentially takes two adjacent extreme points, averages the maximum value and minimum value (or minimum value and maximum value), and generates a floating slice level.

Reference numeral 16 denotes a slice processing section, which uses the floating slice level generated by the floating slice level generation section 15 to perform slicing processing on the barcode read data read from the input data storage section 13. Since the floating slice level is updated for each extreme point, the same slice level is applied between extreme points.

The sliced barcode reading data is output as binary data representing successive bar widths.

[Effect]

The operation of the present invention will be explained using FIG. 2.

FIG. 2 illustrates changes in floating slice levels generated when the present invention is applied to barcode read data.

In the figure, v _i ' is the digitized barcode reading signal, S _r ' is the floating slice level, A to H are the extreme values indicating the maximum or minimum value, and t _A to t _H are the extreme values A to H. This is the extreme point.

Since the floating slice level S _f ' is given by the average value of two adjacent extreme values, the interval between successive extreme points is as follows. Interval Floating slice level S _f ′ t _A −t _B (A+B)/2 t _B −t _C (B+C)/2 t _C −t _D (C+D)/2 t _D −t _E (D+E)/2 t _E −t _F (E+F)/2 t _F −t _G (F+G)/2 t _G −t _H (G+H)/2 In this way, the floating slice level S _f ′ changes from successive maximum values to minimum values or minimum values. Since it is reliably set to a level between the maximum value and the maximum value, and is not affected by the bar width of the barcode or the magnitude of its change, accurate bar width detection is possible.

〔Example〕

FIG. 3 is a block diagram of one embodiment of the present invention.

In the figure, 10 is a barcode scanner, 11
is an amplifier, 12 is an A/D converter, 13 is an input data storage section, 14 is a smoothing processing section, 15 is a floating slice level generation section, 16 is a slice processing section, 17 is a bar width data storage section, 151 is an extreme value Detection unit, 15
2 represents a floating slice level calculation unit, and 153 represents an extreme value storage unit.

The barcode scanner 10 is composed of, for example, a CCD sensor, and scans the barcode surface to output a barcode reading signal whose amplitude changes depending on the reflection level of the black and white bars.

The barcode reading signal is amplified to an appropriate level by an amplifier 11, and then sampled and analog-to-digital converted by an A/D converter 12.
The input data storage unit 13 stores the data in order (hereinafter referred to as barcode reading data).

The smoothing processing unit 14 is activated only when barcode recognition fails, and performs data smoothing processing to remove spike-like noise in the barcode read data stored in the input data storage unit 13 ( (Details will be described later).

In the floating slice level generation section 15, the extreme value detection section 151 detects all extreme values and extreme points from the barcode read data in the input data storage section 13, stores them in the extreme value storage section 153, and then The floating slice level calculation unit 152 calculates each adjacent 2
The floating slice level is obtained by calculating the average value of the extreme values of the two extreme value points, and is supplied to the slice processing section 16 via the extreme value storage section 153. Note that when detecting an extreme value, it is desirable to set a certain threshold value and make a determination in order to ignore small fluctuations.

The slice processing unit 16 includes the input data storage unit 13
The barcode reading data at sequential positions (sampling positions) according to the time series is read from , and each time the position of the extreme point stored in the extreme value storage unit 153 comes, the slice level is updated and the slice is executed. do.

The slice results are binarized for each position (white =
0, black=1) and stored in the bar width data storage section 17, and used for barcode recognition.

Next, the function of the smoothing processing section 14 will be explained.

Barcode reading devices are affected by noise such as dust, scratches, and diffused reflections on the barcode surface, causing cracks in the black bar and spikes in the white bar, resulting in thin white bars and thin black bars, respectively. The problem was that it was incorrectly identified as

If the barcode recognition based on the bar width data in the bar width data storage unit 17 results in an error that the corresponding code does not exist, the smoothing processing unit 14 smoothes the barcode read data stored in the input data storage unit 13. Based on this,
To cause floating slice level generation and slice processing to be redone.

FIG. 4 is an example of noise present in barcode reading data, where _N1 represents a crack and _N2 represents a spike.

The smoothing processing unit 14 is a type of digital filter with a low-pass filter function, and is realized by, for example, sequentially extracting data at a plurality of consecutive positions from barcode reading data as a set and taking a simple moving average. Ru.

FIG. 5 shows an example of smoothing processing in which this is applied to data at each of four consecutive positions, with figure a showing the data before the smoothing process and figure b showing the data after the smoothing process. In the figure, k indicates a sampling position, and v _k indicates a level value of barcode read data at each sampling position k. Further, v _k ′ is its moving average value given by the following equation.

v _k '=1/4 {v _k-1 +v _k +v _k+1 +v _k+2 } Next, an actual example of floating slice level generation by the floating slice level generating section 15 is shown in FIG.
Figure a shows the waveform of the barcode read data _vi , Figure b shows the extreme value point, Figure c shows the data value, Figure d shows the floating slice level, and Figure e shows the bar width data of the slice result.

〔Effect of the invention〕

According to the present invention, since the floating slice level is set at the center of sequentially adjacent extreme values (maximum value and minimum value) regardless of the characteristics of the barcode read data, the level of the barcode read data changes. It is possible to provide a stable and highly reliable barcode reading device that can reliably detect each slope portion of the barcode.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the basic configuration of the present invention, FIG. 2 is an explanatory diagram showing an example of floating slice level generation according to the present invention, FIG. 3 is a diagram showing the configuration of one embodiment of the present invention, and FIG. 4 is a bar code. A waveform diagram showing an example of noise existing in read data, FIG. 5 is an explanatory diagram of an example of smoothing processing, and FIG.
FIG. 7 is an explanatory diagram showing an actual example of floating slice level generation according to the present invention, and FIG. 7 is a waveform diagram showing an example of floating slice level generation by a conventional circuit. In FIG. 1, 12: A/D converter, 13: Input data storage section, 14: Smoothing processing section, 15: Floating slice level generation section, 151: Extreme value detection section, 15
2: Floating slice level calculation unit.

Claims (1)

[Claims] 1. A/D converter 12 that converts an analog barcode reading signal output from a barcode scanner into digital barcode reading data.
an input data storage unit 13 that stores barcode reading data in digital format in the input order; and a slicing level for slicing the barcode reading data based on the barcode reading data stored in the input data storage unit 13. a floating slice level generation unit 15 that generates a floating slice level; and a slice processing unit 16 that reads barcode reading data from the input data storage unit 13 in the order of input and performs slicing using the floating slice level supplied from the floating slice level generation unit 15. The floating slice level generation section 15 includes an extreme value detection section 151 that reads barcode reading data from the input data storage section 13 and detects all local maximum values and local minimum values and extreme point points indicating their positions.
In the barcode reading device having:
Among the local maximum values and local minimum values detected above, two adjacent in time series are sequentially selected, the average value of each two values is determined, and the obtained average value corresponds to the local maximum value and local minimum value. Floating slice level calculation unit 1 outputs as a slice level between two extreme points
52, and for each set of adjacent local maximum values and local minimum values that are sequentially selected on the time series of barcode reading data,
A floating slicing method for a barcode reading device, characterized in that barcode reading data is sliced using the average value as a slicing level between two extreme points of the set. 2. In the floating slice level method of the barcode reading device described in claim 1,
Furthermore, a smoothing processing section 14 is provided, and when the barcode reading device fails to read a valid barcode, the smoothing processing section 14 performs the following operations.
A floating slice method for a barcode reading device characterized in that smoothing processing of barcode read data stored in an input data storage unit 13 is performed, and processing after generation of a floating slice level is redone.