JPH065548B2 - Bar Code Reader Signal Processing Method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a signal processing method for a bar code reader.

(Prior Art) In the signal processing of a conventional bar code reader, as shown in FIG. 6, a bar code 3 is irradiated from a light source 1 through a lens 2 and an optical signal generated by reflected light from the bar code 3 is emitted. The electric / electrical conversion unit 4 converts the analog signal to a pulse-shaped voltage signal, the amplification unit 5 amplifies the analog signal, and the amplified analog signal is input to the comparison unit 6 and the comparison unit 6 outputs the reference voltage. The pulse signal corresponding to the black-and-white bar width of the barcode 3 is converted by comparison with the reference voltage signal from the generator 7, and the obtained pulse signal is input to the decoder 8 for decoding.

However, in such a signal processing method using a bar code reader, in order to improve the resolution, when reading a bar code label printed by a dot printer, a dirty bar code label, or a bar code label having many voids and spots, There was a problem that became difficult.

That is, the barcode 3 printed by the dot printer as shown in FIG. 7 is enlarged as shown in FIG. 8 (A), and is read in the direction of the arrow as shown in FIG. 8 (B).
As shown in FIG. 3, there is a problem that an erroneous pulse occurs at the gap 3b between the dots 3a forming the barcode 3.

Further, in the bar code 3 having the spots 3c and the voids 3d as shown in FIG. 9 (A), when photoelectric conversion is performed at the spot 3c, the waveform becomes as shown in FIG. 9 (B). When the pulse width becomes narrower than the standard, and when the void 3d is converted from light to electricity, the waveform becomes as shown in FIG. 9 (C), and the pulse width becomes thicker than the standard, making it difficult to read correctly. was there.

On the contrary, if the resolution is lowered, there is a problem that the high-density barcode 3 becomes unreadable.

Furthermore, depending on the color of the mount and the shade of the barcode 3,
Since the amplitude of the analog signal changes as shown in FIG. 10 (A), and the amplitude value is below the threshold level,
The number of pulse signals obtained is reduced as shown in FIG. 10 (B), which causes a problem of erroneous reading.

Further, there is a problem similar to the above because the amplitude of the analog signal changes due to the floating of the head portion of the bar code reader.

In order to solve such a problem, recently, the following bar code reading device has been proposed (JP-A-63-19).
6990).

This bar code reader is a means for sampling the output waveform of the light receiving element at minute equal intervals and storing the obtained sampling data string for one unit of bar code, and a noise set based on the estimated noise level. Means for sequentially extracting peak values of waveform peaks and troughs from the sampling data string and describing with their positions, with only fluctuations above the separation level V _N as effective fluctuations, and the number of peaks extracted is defined by the bar code system. Means for reproducing the bar code by binarizing the sample data existing between the peak points on the basis of the average value of the peak values at both ends, and the bar width of the reproduced bar code, on condition that the numbers match And a means for determining that the reproduction bar code is valid, provided that To have.

According to such a barcode reading apparatus, it is possible to read even a barcode printed by a dot printer or the like.

(Problems to be Solved by the Invention) However, in such a conventional barcode reading apparatus, when half of the barcode to be read is dirty,
There was a problem that the barcode signal at that portion could not be reproduced correctly. That is, the read signal obtained in this case is
As shown in FIG. 11, the level of the read signal obtained by reading the dirty portion is low as a whole from the right half of the figure, and the level of the read signal obtained by reading the unclean portion is shown in FIG. As is apparent from the left half of the figure, the sampling data string obtained by sampling such a read signal as a whole has a peak value of waveform peaks and valleys with only fluctuations above the noise separation level V _N as effective fluctuations. In the case of extracting, the level in the right half of FIG. 11 is lower than V _{N as a} whole, so that there is a problem that the bar code signal cannot be reproduced correctly.

Further, in this conventional bar code reader, the noise separation level V _N after the reading is started is changed to the new noise separation level V _N ′, but this new noise separation level V _N ′.
Calculates the level variation ΔV in the front blank part of the barcode and sets it at a position lower than the reference white level V _O by 3 × ΔV. Therefore, if the latter half of the barcode array is stained,
_'Than defining the, than the latter half portion signal level of the read signal has dropped overall the like FIG. 11, much new noise isolation level V _N' new noise isolation level V _N at the first half changed to However, there was a problem that the bar code signal could not be reproduced correctly.

An object of the present invention is to provide a signal processing method for a bar code reader that can correctly reproduce a bar code signal even if the latter half of the bar code is dirty.

(Means for Solving the Problem) The means of the present invention for achieving the above object will be described below.

The invention according to claim (1) is a signal processing method by a bar code reader when the number of bar codes is fixed, and an optical signal by reflected light from the bar code is converted into an analog signal by optical / electrical conversion. The signal is converted into a signal, the analog signal is sampled, converted into a multilevel digital signal according to a change in the crest level thereof, and then stored in a memory, and the maximum of the multilevel digital signal stored in the memory is stored. obtain the maximum value V _max and the difference V _w of the minimum value V _min of the minimum value of the values, the V _{w /} 2 that the V _w 1/2 and the standard amplitude K initially store the memory Each inflection point at which the sign of the slope of the envelope waveform of the multilevel digital signal is inverted is detected, and if the amplitude between adjacent inflection points is greater than or equal to the standard amplitude K, the inflection point is detected. Set inflection point as extreme value Regarded as waveform corresponding envelope waveform of the multilevel digital signal on the bar code,
If the amplitude between the adjacent inflection points is smaller than the standard amplitude K, it is regarded as noise that does not correspond to the bar code and is not judged as an extreme value, and then the envelope waveform of the digital signal that corresponds to the bar code. Waveform shaping is performed so that the amplitude between the adjacent maximum and minimum values of each becomes constant, and the midpoint between the maximum and minimum values of the obtained envelope waveform is set as the threshold level. Converted to a pulse signal of a value level, the margin before and after the barcode is determined by the pulse signal, the number of the barcode existing between the margins before and after the barcode is counted, and the counted number is the number of the barcode. Compared with the specified number of barcodes specified by type, a. When the number of counts is larger than the specified number, the value of K is changed again by the following equation (1), and K (n) = K (n-1) + ( _Vw / ²ⁿ ) ... (1 ) However, n represents the number of repetitions.

B. When the counted number is less than the specified number, the value of K is changed again by the following formula (2), and K (n) = K (n-1)-( _Vw / ²ⁿ ) ... (2) It is characterized in that the pulse signal at that time is decoded when the number of counts matches the specified number by repeating steps a and b.

According to the invention of claim (2), the number of barcodes is not fixed, and the counting of the barcodes is a + bm.
(Where a and b are constants determined by the type of the barcode, m is the number of characters), in the signal processing method by the barcode reader, the optical signal generated by the reflected light from the barcode is converted into an optical signal. After conversion into an analog signal, the analog signal is sampled and converted into a multilevel digital signal according to a change in the crest level, and then stored in a memory, and the multilevel digital stored in the memory. Obtain a difference V _w between the maximum value V _{max of the} signal maximum values and the minimum value V _min of the minimum values,
First, V _w / 2 is used as the value of K to obtain a standard amplitude K, and inflection points at which the signs of the slopes of the envelope waveforms of the digital signals of the multilevel digital signals stored in the memory are inverted are detected. If the amplitude between the adjacent inflection points is equal to or larger than the standard amplitude K, the envelope waveform of the digital signal of the multi-valued level having the inflection point as an extreme value is regarded as the waveform corresponding to the bar code. If the amplitude between the adjacent inflection points is smaller than the standard amplitude K, it is regarded as noise not corresponding to the bar code and is not judged as an extreme value, and then the envelope waveform of the digital signal corresponding to the bar code. Waveform shaping is performed so that the amplitude between the adjacent maximum and minimum values of each becomes constant, and the midpoint between the maximum and minimum values of the obtained envelope waveform is set as the threshold level.
Convert to a pulse signal of a value level, determine the margin before and after the bar code by the pulse signal, count the number of the bar code existing between the margins before and after the bar code, The value of the character number m of a + mb is obtained, the true bar code number is assumed using the value of the character number, and the true bar code number based on the assumption is compared with the counting number to calculate the value of K. If the count number of the bar code according to the K value after each change and the true bar code number according to the assumption match, the pulse signal is decoded and the K value is changed several times. If the numbers do not match, the value of the character number m is changed to a value next closer to it, the true number of barcodes is again assumed, and the same processing is repeated.

(Operation) In claims (1) and (2), the maximum value V _max and the minimum value among the maximum values of the multi-level digital signal stored in the memory by reading the bar code, sampling it, converting it into a digital signal, and storing it in the memory. Difference V _w of the minimum value V _min among these values is obtained, and V _w / 2 obtained by halving this V _w is set as a standard amplitude K, and the sign of the slope of the envelope waveform of the multilevel digital signal is inverted. The inflection point is detected and the amplitude between adjacent inflection points is the standard amplitude K.
If it is above, the envelope waveform of the digital signal of the multivalued level having the inflection point as the extreme value is regarded as the waveform corresponding to the bar code, and the amplitude between the adjacent inflection points should be smaller than the standard amplitude K. For example, since the waveform corresponding to the barcode is extracted by taking the method of considering the nozzle as not corresponding to the barcode, the barcode can be properly reproduced even if the latter half of the barcode is dirty.

In particular, in claim (1), when the number of counts does not match the specified number, the standard amplitude K is repeatedly changed only n times. Therefore, when the number of bar codes is fixed, The standard amplitude K can be automatically changed appropriately according to the bar code, and noise can be easily removed.

Further, in claim (2), the margin before and after the barcode is determined by the pulse signal of the barcode obtained by removing the noise, and the number of barcodes existing between the margins before and after is counted, Closest to the number of counts (a + m
The value of the character number m in b) is calculated, the true bar code number is assumed using the value of the character number, the true bar code number based on the assumption is compared with the counting number, and the value of the standard amplitude K is obtained. Is changed several times, the standard amplitude K when the number of bar codes is not fixed is automatically changed according to the bar code, and noise can be easily removed.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a signal processing apparatus for carrying out the method of the present invention. In the signal processing method of the bar code reader of this embodiment using such a device, the light source 1 irradiates the bar code 3 as shown in FIG. An optical signal generated by light is converted into an analog signal S as shown in FIG.
1, and the analog signal S1 is amplified by the amplification unit 5,
The amplified analog signal S1 is sampled by a sample hold circuit section (hereinafter referred to as S / H section) 9, and then an analog / digital conversion section (hereinafter referred to as A / D conversion section) 10 has a peak level of the analog signal S1. Multi-level digital signal D as shown in FIG. 2 (C) according to changes
It is converted into 1 and input to a central processing unit (hereinafter referred to as CPU) 11. On the other hand, the analog signal S1 from the amplification unit 6 is converted into a pulse signal through the comparator 12 and converted into a CPU 11
To enter.

The CPU 11 temporarily stores in the memory 13 only the multilevel digital signal D1 input from the bar portion of the barcode 3 by the pulse signal of the comparator 12 in order to effectively use the memory 13. An inflection point at which the sign of the slope of the envelope waveform of the multilevel digital signal D1 stored in the memory 13 is inverted is detected. If the amplitude between adjacent inflection points is equal to or greater than the standard amplitude K, the inflection points are set to extreme values P1, P2, P3, ... As shown in FIG. The envelope waveform of the signal D1 is regarded as the waveform corresponding to the barcode 3. If the amplitude between adjacent inflection points is smaller than the constant K, it is regarded as noise that does not correspond to the barcode 3 and is not judged as an extreme value and ignored.

Next, the waveform between the extreme values P1, P2, P3, ... Of the envelope waveform of the digital signal D1 corresponding to the bar code 3 is enlarged or reduced as shown in FIG. Between minimum values, that is, between P1-P2, between P2-P3, P3-P
4 and between P4 and P5, between P5 and P6, etc., waveform shaping is performed so as to have a constant amplitude X, and a waveform shaped digital signal D2 is obtained.

For example, in the case of FIG. 3 (A), since the amplitude is smaller than the amplitude X between the extreme values P1 and P2, the extreme value P2 is enlarged by the equal magnification α.
Since it is larger than the amplitude X between P3, it is reduced by an equal magnification β, between the extreme values P4 and P5, it is reduced by an equal magnification γ because it is larger than the amplitude X, and between extreme values P5 and P6, it is smaller than the amplitude X and is equal magnification η. Expanding. Here, the equal magnifications α, β ... Are determined as follows.

α = (amplitude between extreme values P1 and P2) / X β = (amplitude between extreme values P2 and P3) / X ... Maximum values P2 and P4 of the waveform of the shaped digital signal D2
, And the minimum values P1, P3, ... As threshold levels SL, they are converted into binary level pulse signals PS as shown in FIG. 3 (C).

The pulse signal PS is decoded into various bar codes, and communication processing is performed with the host computer according to various interface specifications.

Next, how to calculate the value of the standard amplitude K will be described with reference to FIG.

Multilevel digital signal D stored in the memory 13
The difference V _w between the maximum value V _max and the minimum value V _{min of} 1 is obtained, and V _w / 2 is first used as the value of K (step ST1). The detection of the extreme value as described above (step ST2), the waveform Signal processing of shaping (step ST3) and binarization (step ST4) is performed to obtain a pulse signal PS.

Next, the margins M1 and M2 of the bar code 3 are determined by the pulse signal PS as shown in FIG. 5, and the bar code 3 existing between these margins M1 and M2 is determined.
, And compares the counted number with the specified number of barcodes 3 specified by the type of barcode 3 (step ST5), and performs the following processing.

(A) When the number of barcodes 3 is fixed.

(A-1) When the number of counts is more than the specified number, the value of (repetition processing number n = 2) K is changed again by the following equation (1) (step ST5), and K (n) = K (n -1) + (W _w / 2 ⁿ ) ... (1) (A-2) When the number of counts is less than the specified number,
It is changed again by the following equation (2) of (n = 2) K, (step ST5), K (n) = K (n-1)-( _Vw / ²ⁿ ) ... (2) These (A-1 ), K changed based on (A-2)
The calculation of the value of K is repeated until the number of counts of the bar code 3 matches the specified number by the value of. When the numbers of the bar codes 3 match, the pulse signal PS at that time is decoded.

It should be noted that the upper limit of the number of times of repeating processing n is set to 2 to 3 times, and if the number of counts does not match the specified number during that time, an error occurs.

(B) When the number of barcodes 3 is not fixed.

In this case, the number of counted barcodes 3 is a + mb (where a and b are constants determined by the type of barcode 3,
m: number of characters), the number of characters of the barcode 3 is a + mb, and when the number of characters m is changed, the closest value of the number of characters m is obtained, and the value of m is used to determine the true barcode. The number is assumed. The number of true bar codes assumed from this and the number of counts are compared (step ST5), and the value of K is changed according to the constants a and b (step ST5).

If the counted number of barcodes 3 does not match the true number of barcodes due to the changed value of K, the calculation of the value of K is repeated several times.

The upper limit of the number of times n of this iterative processing is set to 2 to 3 times, and if the values do not match in the meantime, m is moved to the next closest value and the same processing is performed. If the values do not match, an error occurs.

When the numbers of the bar codes 3 match, the pulse signal PS at that time is decoded (step ST6).

The decoded signal is compared with the waveform of the check bit previously displayed on the bar code to determine whether the signal waveform is correct.

The check bit may be used to determine whether it is correct or not by using a pulse signal before decoding.

In the present invention, the value of K is not only V _w / 2, but V _w / 4.
Etc. can be changed depending on the characteristics of the photoelectric conversion unit 4, the amplification unit 6, and the like.

Further, as a bar code reader to which the present invention can be applied,
In addition to pen-type bar code readers, there are CCD touch scanners, laser scanners, and the like.

(Effects of the Invention) As described above, according to the signal processing method for the bar code reader of the present invention, the following effects can be obtained.

According to the inventions of claims (1) and (2), the maximum value V _max and the minimum value of the maximum values of the multi-level digital signals stored in the memory by reading the bar code, sampling it, converting it into a digital signal, and storing it in the memory. Obtain the difference V _w of the minimum value V _min of the values,
The V _{w /} 2 that the V _w 1/2 the standard amplitude K, detecting an inflection point where the sign of the slope of the envelope waveform of the multivalued level of the digital signal is inverted, between adjacent inflection points Is greater than the standard amplitude K, the envelope waveform of the digital signal of the multi-valued level having the inflection point as an extreme value is regarded as the waveform corresponding to the bar code, and the amplitude between the adjacent inflection points is determined. Is smaller than the standard amplitude K, the nozzle corresponding to the bar code is regarded as a nozzle and the waveform corresponding to the bar code is extracted. Therefore, even if the latter half of the bar code is contaminated, the bar code Playback can be performed.

Particularly, in the invention described in claim (1), when the number of counts does not match the specified number, the standard amplitude K is changed repeatedly n times, so that the number of bar codes is fixed. When the standard amplitude K is present, the standard amplitude K can be automatically changed according to the bar code, and noise can be easily removed.

In the invention described in claim (2), the margin before and after the barcode is determined by the pulse signal of the barcode obtained by removing the noise, and the number of barcodes existing between the margins before and after is determined. Counting, the value of the character number m of (a + mb) closest to the counted number is obtained, the true bar code number is assumed using the value of the character number, and the true bar code number and the counted number are calculated based on the assumption. Since the value of the standard amplitude K is changed several times by comparing the above, the standard amplitude K can be automatically and appropriately changed according to the bar code when the number of bar codes is not fixed, and noise can be removed. It can be done easily.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a signal processing apparatus for carrying out the method of the present invention, and FIGS. 2 (A), (B) and (C) are enlarged views of a bar code and an analog obtained from the bar code. A signal waveform diagram and a waveform diagram of a multilevel digital signal obtained from the analog signal, FIGS. 3A, 3B, and 3C are explanatory diagrams of the extreme value of the multilevel digital signal, and FIG. A waveform diagram in which a digital signal is enlarged and reduced and waveform-shaped, a waveform diagram of a pulse signal obtained from the waveform-shaped digital signal, and FIG. 4 is a flow chart diagram showing each step of signal processing in the present embodiment, FIG. 5 is an explanatory view of the margin of the bar code, FIG. 6 is a block diagram of a conventional signal processing device,
FIG. 7 is an explanatory view of the bar code, FIG. 8 (A) is an enlarged view of the bar code shown in FIG. 7, and FIG. 8 (B) is FIG. 8 (A).
Waveform diagram when scanning the arrow part of the bar code shown in
FIG. 9 (A) is an enlarged view of a bar code having spots and voids, FIG. 9 (B) is a waveform diagram when the spot portion of FIG. 9 (A) is read, and FIG. 9 (C) is Figure 9 (A)
Waveform diagram when reading the voids in Fig. 10 (A)
FIG. 11B is a waveform diagram of an analog signal obtained from a conventional bar code having a small relative reflection and a large level change, and a pulse signal obtained from the analog signal. FIG. 11 is a bar code having a dirty second half. It is a waveform diagram of the signal read. 1 ... Light source, 2 ... Lens, 3 ... Bar code, 3a ... Dot, Sb ... Gap, 3c ... Spot, 3d ... Void, 4 ... Photoelectric conversion part, 5 ... Amplification part , 6 ... comparison section, 7 ... reference voltage generation section, 8 ... decoder, 9 ... sample hold circuit section (S / H section), 10 ... analog / digital conversion section (A / D conversion section),
11 ... Central processing unit (CPU), D1 ... multi-level digital signal, D2 ... waveform-shaped digital signal, P1, P2, P3 ... extreme value, S1 ... analog signal, 12 ... comparator, 13 ... Memory.

Claims (2)

[Claims] 1. A signal processing method using a bar code reader when the number of bar codes is fixed.
The optical signal resulting from the reflected light from the bar code is converted into an analog signal by optical / electrical conversion, the analog signal is sampled, converted into a multilevel digital signal according to the change in the crest level, and then stored in a memory. Then, the difference V _w between the maximum value V _max of the maximum values and the minimum value V _min of the minimum values of the multi-level digital signals stored in the memory is obtained, and first, the V _w is 1 / V _w / 2 set to 2 is set as the standard amplitude K, and the inflection points at which the signs of the slopes of the envelope waveforms of the multilevel digital signals stored in the memory are inverted are detected, and the adjacent inflections are detected. If the amplitude between the points is equal to or larger than the standard amplitude K, the envelope waveform of the digital signal of the multi-level having the inflection point as an extreme value is regarded as the waveform corresponding to the barcode, and the adjacent variable The amplitude between the inflection points Serial without determining an extreme value is regarded as a standard amplitude K is smaller than not correspond to the barcode noise,
Next, the waveform between the adjacent maximum value and minimum value of the envelope waveform of the digital signal corresponding to the barcode is enlarged or reduced so as to have a constant amplitude.
The midpoint of the maximum value and the minimum value of the obtained envelope waveform is converted into a binary level pulse signal as a threshold level, the margin before and after the bar code is determined by the pulse signal, and the margin before and after the barcode is determined. The number of the above-mentioned bar codes existing between them is counted, and the counted number is compared with the specified number of the bar codes specified by the kind of the bar code. When the number of counts is larger than the specified number, the value of K is changed again by the following equation (1), and K (n) = K (n-1) + ( _Vw / ²ⁿ ) ... (1 ) However, n represents the number of repetitions. B. When the counted number is less than the specified number, the value of K is changed again by the following formula (2), and K (n) = K (n-1)-( _Vw / ²ⁿ ) ... (2) A signal processing method of a bar code reader, characterized in that the pulse signal at that time is decoded when the number of counted lines matches the specified number by repeating steps a and b. 2. The number of barcodes is not fixed, and the counting of the barcodes is a + bm (however,
a, b: constants determined by the type of barcode, m:
In the signal processing method by the bar code reader when there is a relationship of (character number), the optical signal by the reflected light from the bar code is converted into an analog signal by optical / electrical conversion, the analog signal is sampled, and its peak level is obtained. The maximum value V of the maximum values of the multilevel digital signals stored in the memory after being converted into a multilevel digital signal according to the change
The difference V _w between _max and the minimum value V _min of the minimum values is obtained, and first, V _w / 2 is used as the value of K to obtain the standard amplitude K, and the digital signal of the multi-value level stored in the memory is obtained. The inflection points at which the signs of the slopes of the envelope waveforms are inverted are detected, and if the amplitude between the adjacent inflection points is greater than or equal to the standard amplitude K, then the multivalued value having that inflection point as the extreme value The envelope waveform of the digital signal of the level is regarded as a waveform corresponding to the bar code, and if the amplitude between the adjacent inflection points is smaller than the standard amplitude K, it is regarded as noise that does not correspond to the bar code and is regarded as an extreme value. Without making a judgment, next, waveform shaping is performed such that the amplitude between the adjacent maximum value and minimum value of the envelope waveform of the digital signal corresponding to the barcode becomes a constant amplitude, respectively, and the obtained value is obtained. Of the maximum and minimum values of the generated envelope waveform Converting the midpoint into a binary level pulse signal with a threshold level, determining the margin before and after the bar code by the pulse signal, counting the number of the bar code existing between the margins before and after,
The value of the character number m of a + mb that is closest to the counted number is obtained, the true bar code number is assumed using the value of the character number, and the true bar code number and the counted number based on the assumption are calculated. In comparison, the K value is changed several times, and when the count number of the bar code according to the K value after each change and the true bar code number according to the assumption match, the pulse signal at that time is decoded. , K several times
If the values do not match even after the value is changed, the value of the number of characters m is changed to a value that is the next closest, the true number of bar codes is again assumed, and the same process is repeated. Signal processing method.