JPS6363949B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a serial signal correction method, and more particularly to a serial signal correction method for correcting distortion when the width of "1" and "0" of a transmission signal is more than the normal value. It is something.

For example, when reading a bar code with an optical hand scanner or fixed scanner and transmitting it, the transmitted signal may be more distorted than the normal signal. Furthermore, in bar codes, the bar width is often distorted even during printing. This is especially noticeable when printing is done manually using a hand labeler. However, even when printed in this manner, the bar width tends to become thicker or thinner almost uniformly.

When a bar code like the one shown in Figure 1 is read out by an optical device such as a fixed scanner and transmitted, the receiving side sets the part corresponding to the black bar as "1".
The part corresponding to the white bar is set to "0", and the width corresponding to the bar code is set to "1", respectively.
It is received as a “0” signal. Therefore, when receiving this in a normal state, it is a signal as shown in Figure 2 A, that is, it is a signal of "1" and "0" whose width corresponds to the width of the black bar and white bar of the bar code. Receive this as a signal. However, if the received signal is more distorted than the normal signal for some reason, for example, as shown in Figure 2 (b), the rising and falling parts of the "1" signal indicating the width of the black bar will be distorted. As a result, the receiving side receives the black bar as having a narrow width and the white bar as having a wide width. However, the bar as shown in Figure 1.
The code has a plurality of widths of black bars and widths of white bars, and is configured to display a specific number or the like by combining a plurality of each of these black bars and white bars. Therefore, if the width of the received "1" and "0" is different from the normal width due to this signal distortion, a bar code reading error will occur, and as a result, the bar code cannot be read accurately. The problem is that it cannot be done.

Therefore, in order to solve these problems, the present invention normalizes the received signal by detecting the amount of distortion when there is distortion in the received signal and correcting the received signal based on this amount of distortion. It is an object of the present invention to provide a serial signal correction method that performs the following steps. To this end, the serial signal correction method of the present invention includes period detection means for detecting high-level periods and low-level periods of the signal, reference signal detection means for detecting the reference signal, and multiple a signal holding means, a correction amount generating means for generating a correction amount based on the reference signals held in the plurality of signal holding means, an adding section for adding the correction amount to the input signal, and a correction amount generating section for adding the correction amount to the input signal. and a selection section that selects and outputs the outputs of the addition section and the subtraction section corresponding to the input signal, and calculates the correction amount of the input signal based on the input reference signal and performs this correction. It is characterized in that the input signal is corrected by adding or subtracting a quantity to the input signal.

Before describing the present invention in detail based on examples,
The principle of operation will be explained based on FIG.

For example, when a regular bar code signal is received on the receiving side in the state shown in Figure 2 A, or when it is distorted in the state shown in Figure 2 B, the black label signal B on the transmitting side is ₀ , _B1 , _B2 ...
The label widths A, C, E... of ... are a,
The label widths B, D... of the white label signals W ₀ , W ₁ ... on the transmitting side change to b, d... on the receiving side. Even when subjected to such distortion, the length L from the fall of the black label signal B ₀ ′ in Figure 2B to the fall of the next black label signal B ₁ ′ is the same as the normal one in Figure 2A. In the case of a black label signal, the length L from the falling edge of the black label signal B ₀ to the falling edge of the next black label signal B ₁ is used. It is well known that the accuracy of
This is also stipulated by JIS). Of course, this also applies to the rise.

Therefore, in Figure 2 A, the black label signal
When B ₀ , white label W ₀ , and black label signal B ₁ are used as reference signals such as guard bars, the following equation holds true.

A+B=a+b...B+C=b+c...+=A+2B+C=a+2b+c...In the case of the reference signal, A=B=C, so C=1/4(A+2B+C)=1/4(a+2b+c)...Now When the label width of the white label signal _W1 is D and the reception width when this is received is d, the following equation holds true.

D+C=d+c... D=-C+d+c=d+{-1/4(a+2b+c)+c}... ∴D=d+1/4(3c-2b-a)... Also, the label width of black label signal B ₂ is E If the signal width when this is received is e, the following equation holds true.

E+D=e+d... E=-D+e+d=-{d+1/4(3c-2b-a)} +e+d ∴E=e-1/4(3c-2b-a)... Therefore, from the above formula and formula As is clear, by adding the correction amount 1/4 (3c-2b-a) obtained from the reference signal to the white label signal, and by adding the correction amount 1/4 obtained from the reference signal to the black label signal.
A normalized signal can be obtained by subtracting (3c-2b-a). Note that 3c-2b-a<0 in the case of the states a and b of FIG. 2. 3c−2b if the black bar becomes thicker
−a>0.

Next, an embodiment of the present invention will be described based on FIG. 3 and with reference to FIG. 2.

In the figure, 1 is an edge detection circuit, 2 is a signal width count circuit, 3 is a first buffer, 4 is a reference signal detection section, 5 is a gate, 6 is a second buffer, 7 is a third buffer, and 8 is a fourth buffer. , 9 is a correction amount generation circuit, 10 is an addition section, 11 is a subtraction section, and 12 is a selection section.

The edge detection circuit 1 detects the rising and falling portions of the transmitted signal, and outputs "1" at this time.

The signal width count circuit 2 receives the black label signal B ₀ ′,
The signal widths a, c, e... of B ₁ ', B ₂ '... and the signal widths b, d... of the white label signals W ₀ ', W ₁ '... are measured.

The first buffer 3 is a buffer in which the received signal to be corrected is temporarily set.

The reference signal detection section 4 detects whether the received signal is a reference signal such as a guard bar or center bar, and is a known device. For example, in the case of a guard bar, the black label signal B ₀ , white label signal W ₀ , and black label signal B ₁ are all composed of A, B, and C of the same length, so when receiving Even _{if there} is distortion _in Detects that it is a reference signal. Alternatively, a center bar may be used as the reference signal. As this detection method, for example, similar to guard bar detection, white label signals W _{0 ′} , W _{1 ′} ,
Detect the existence of W ₂ ′. As will be described later, when the reference signal is set in the second buffer 6 to fourth buffer 8, the gate 5 is controlled to be turned off.

A reference signal is set in the second buffer 6 to fourth buffer 8, and these second buffer 6 to fourth buffer 8 constitute a plurality of signal holding means. 4th buffer 8 is black label signal
The length a of B ₀ ' is set, the length b of the white label signal W ₀ ' is set in the third buffer 7, and the length c of the black label signal B ₁ ' is set in the second buffer 6. It is something that

The correction amount generation circuit 9 is connected to the second buffer 6 to the fourth buffer.
Based on the value of the reference signal set in the buffer 8, the correction amount 1/4 (3c-2b-a) is calculated and output.

The adder 10 adds the correction amount 1/4 (3c-2b-a) output from the correction amount generation circuit 9 to the length value of the received signal transmitted from the first buffer 3.

The subtraction unit 11 calculates the correction amount 1/4 (3c-2b-
a) is subtracted.

The selection unit 12 selectively outputs the signal transmitted from either the addition unit 10 or the subtraction unit 11, and when “0” is applied to the selection signal terminal S, the selection unit 12 outputs the signal transmitted from the subtraction unit 11 when “0” is applied to the selection signal terminal S. On the other hand, when "1" is applied to the selection signal terminal S, the value transmitted from the adder 10 is output.

Next, the operation shown in FIG. 3 will be explained.

Now, when the first rising edge of the black label signal B ₀ ', which is the received signal, is transmitted at time t ₀ in FIG. 2B, the edge detection circuit 1 detects this and outputs "1". As a result, the signal width counting circuit 2 starts a counting operation based on a clock source (not shown). Then, at time t ₁ , the black label signal
When B ₀ ' ends, its falling edge is detected by the edge detection circuit 1, and the signal width counting circuit 2 outputs the length a of the black label signal B ₀ ' counted up to that time. , this a is set in the first buffer 3. Further, the signal width counting circuit 2 is reset by the output "1" from the edge detection circuit ₁ at this time t1, and starts counting operation to measure the length of the white label signal _W0 '. Then, at time _t2 , when the white label signal _W0 ' ends and the edge detection circuit 1 detects the rising edge of the black label signal _B1 ' and outputs "1", the above signal set in the first buffer 3 a is set in the second buffer 6 via the gate 5, and the length b of the white label signal W ₀ ' transmitted from the signal width counting circuit 2 is set in the first buffer 3. Then, the signal width count circuit 2 is reset once,
We will start measuring the length of the black label signal B ₁ '.

These steps are performed in sequence, and at time _t4 , a is set in the fourth buffer 8, b is set in the third buffer 7, c is set in the second buffer 6, and d is set in the first buffer 3. When the reference signal detection unit 4 recognizes that the signals a, b, and c that have been sequentially outputted from the first buffer 3 are the gated bars, which are one of the reference signals, Control 5 off. At this time, in the correction amount generation circuit 9, the second buffer 6
or said a transmitted from the fourth buffer 8;
Since the correction amount 1/4 (3c - 2b - a) is calculated and output based on b and c, the adder 10 calculates d + 1/4 (3c - 2b - a) and outputs the result. The section 11 performs the calculation of d-1/4 (3c-2b-a), outputs the result, and transmits it to the input terminals P and Q of the selection section 12, respectively. At this time, since the black label signal B ₂ ' is transmitted to the edge detection circuit 1, "1" is applied to the selection terminal S of the selection section 12, so that the selection section 12 receives the output from the addition section 10. It will output d+1/4(3c-2c-a). Then, when the next white label signal is transmitted to the edge detection circuit 1, the selection terminal S
Since "0" is applied to , the selection section 12 outputs e-1/4 (3c-2b-a), which is obtained by correcting e set in the first buffer 3 by the subtraction section 11. It turns out.

In this way, the selection unit 12 sequentially outputs distortion-corrected received signals, and based on this, the received signals can be accurately identified.

Note that in the above explanation, the reference signal is composed of three signals, but the reference signal is a black label signal with the same signal width (the signal width is
A′) and a white label signal (signal width B′) can be corrected in the same way. In this case, A'=B', so if the widths of these received signals are a' and b', the following equation holds true.

A′+B′=a′+b′, Similarly, the received signal width of label signals C′, D′, and E′ is
If c′, d′, e′, B′+C′=b′+c′, C′+D′
=c′+
d'... is.

Since the time from rise to rise (or from fall to fall) of the signal is the same on both the transmitting side and the receiving side, the following equation holds.

A′=B′ ∴B′=1/2(a′+b′) …… B′+C′=b′+c′ ∴C′=b′+c′−B′ =c′+b′−1/2(a′+b′) ∴C′=c′+1/2(b′−a′) …… Also D′=c′+d′−C′ =c′+d′−{c′+1/2(b′−a′)} ∴D′=d′−1/2(b′−a′) …… Similarly, the following equation holds true.

E'=d'+e'-D'=e'+1/2 (b'-a')... Therefore, the correction value of the black level signal (high level) is 1/2 (b'-a') and White level signal (low/
By adding a correction value -1/2 (b'-a') of (level) to the time width of the measured waveform, it can be converted into a normalized waveform.

Therefore, as explained above, according to the present invention, a normalized signal can be obtained by detecting a reference signal, determining the correction amount based on it, and adding it to the measured waveform, so that reception can be performed very accurately. Be able to identify signals. Therefore, the recognition rate of the received signal can be greatly improved and, for example, bar codes can be interpreted accurately and accurate data can be obtained based on this. Although the above description has been made regarding a bar code signal, the present invention is of course not limited to this.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a bar code, Fig. 2 A is an ideal bar code reading waveform, Fig. 2 B is a received waveform with distortion, and Fig. 3 is the configuration of an embodiment of the present invention. be. In the figure, 1 is an edge detection circuit, 2 is a signal width count circuit, 3 is a first buffer, 4 is a reference signal detection section, 5 is a gate, 6 is a second buffer, 7 is a third buffer, and 8 is a fourth buffer. , 9 is a correction amount generation circuit, 10 is an addition section, 11 is a subtraction section, and 12 is a selection section.

Claims (1)

[Claims] 1. Period detection means for detecting a high level period and a low level period of a signal, a reference signal detection means for detecting a reference signal, and a plurality of signal holding means for temporarily holding the reference signal; a correction amount generating means for generating a correction amount based on the reference signals held in the plurality of signal holding means; an addition section for adding the correction amount to the input signal; and a subtraction section for subtracting the correction amount from the input signal. , a selection unit that selects and outputs the output of the adder and the subtracter in response to the input signal, calculates a correction amount for the input signal based on the input reference signal, and applies this correction amount to the input signal. A serial signal correction method characterized by correcting an input signal by performing addition or subtraction.