JP2826226B2 - Read signal processing method of record slip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects a quantization error generated by digital processing (quantization processing) of a read signal output according to a code width of a record slip such as a bar code. The present invention relates to a method for processing a read signal of a record slip.

[0002]

2. Description of the Related Art Bar code readers for reading bar codes recorded on bar code labels have been developed. The barcode reader optically reads a barcode recorded on the label by a photoelectric conversion element and outputs an electric signal corresponding to the width of the barcode. The output electric signal is subjected to signal processing by predetermined processing means, and the width of the bar code and the interval between the bar codes are detected.

For example, analog processing shown in FIG. 3 is known as one of a series of signal processing methods. That is, first, a differentiation circuit or the like performs a differentiation process on a read signal 101 read and output by a reading unit such as a photoelectric conversion element corresponding to the pattern of the bar code 100, thereby forming a differentiation processing signal 102. . Next, in the differential processing signal 102, an extreme value, that is, a minimal value M ₁ and a maximal value M ₂ are respectively detected, and the minimal value M ₁ is detected.
_The bar width signal 103 is formed by calculating the difference between the coordinate values x ₁ and x ₂ between ₁ and the maximum value M ₂ , whereby the thickness L of the bar code is recognized. By the way, in the signal processing by such an analog method, the thickness (width) of a bar can be accurately detected, but it is difficult to remove the noise when noise occurs. There are disadvantages such as difficulty in storing data.

Therefore, signal processing by a digital method has been developed. That is, in FIG.
A / D conversion means forms a quantized signal 104 based on the read signal 101 read according to the pattern 00 (see FIG. 3). A predetermined process is performed based on the quantized signal 104, that is, a difference process for obtaining a difference between adjacent pixels is performed, and coordinate (position) values corresponding to the peaks 105 and 106 of the difference value are detected as bar boundary positions. , A bar width signal 103 '. Thereby, the thickness L 'of the bar is recognized.

[0005]

In the signal processing by such a digital method, when forming a quantized signal, the sampling interval of the quantized data is not unique, and therefore cannot be ignored depending on the interval. A large quantization error occurs. Accordingly, an object of the present invention is to provide a method of processing a read signal of a recording slip which can minimize the occurrence of quantization errors in digital signal processing in view of the above-mentioned conventional disadvantages. .

[0006]

That is, according to the present invention, an analog signal output from a reading means for reading a code recorded on a record slip is quantized into a digital signal by an A / D conversion means, and then the digital signal is quantized. Performing a difference processing of the digitized digital signal and outputting a signal at a coordinate interval according to the code width. The correction is performed according to the value of the ratio of the difference values between the preceding coordinate section immediately before the main coordinate section that gives the maximum difference value and the immediately succeeding coordinate section, and the boundary coordinate value corresponding to the boundary portion of each code is calculated. It is configured to be determined. Further, in the present invention, the difference values of the quantized digital signals in the coordinate section and the subsequent coordinate section are set to Δy ₁ and Δy ₂ , the start position coordinate of the main coordinate section is set to x, and the value of the main coordinate section is set to Δx. At this time, the boundary coordinate value x ′ is calculated by the following correction expression x ′ = x + Δx ·
It is determined by [Δy ₂ / (Δy ₁ + Δy ₂ )].

[0007]

According to the recording signal reading signal processing method of the present invention, the correction formula (weight function) considering the value of the ratio of the difference values in the section immediately before and immediately after the main coordinate section is used. The width from the start point position to the boundary coordinate value is determined. For example, if the difference value in the section immediately after the main coordinate section is larger than the difference value in the immediately preceding section, the width is determined according to the ratio of the difference values. The quantization error is corrected by shifting the boundary coordinate value to the rear side where the difference value is larger than the center of the main coordinate section by an amount.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a method of processing a read signal of a recording form according to the present invention. In the method of processing a read signal of a recording form, an analog read signal 2 output according to a pattern of a bar code 1 is quantized. The quantization error generated when the digital signal 3 is converted into a digital signal 3 is corrected in accordance with a program stored in advance, that is, by the following method to form a bar width signal 4 and a pattern of the bar code 1,
That is, the thickness (width) of the bar code 1 and the bar code interval are read as accurately as possible.

That is, in this correction method, FIG.
First, a point to which an x coordinate (boundary coordinate value) corresponding to the boundary of either the start or end of the barcode 1 is given, that is, the inflection point A
It detects a section including S ₁ (hereinafter referred to as a main coordinate interval). Next, in the sections immediately before and after the section S ₁ (hereinafter referred to as the preceding coordinate section S ₂ and the subsequent coordinate section S ₃ ), a difference value between the quantization points P ₁ is obtained.
When determining the difference in the y direction in the graph 3 connecting the respective quantization points shown in FIG. 2 '(hereinafter this is called quantization curve), the coordinates before section S _2, for example, [Delta] y ₁ = y ₂ -y ₁ (However, the first quantization point P ₁ and the second quantization point P ₁
The y-coordinate of the quantization point P ₂ is defined as y ₁ and y ₂ , respectively. ) For post-coordinate section S _{3, like, Δy 2 = y 4 -y 3} ( provided that the third quantization point P ₃ and the fourth
The y-coordinate of the quantization point P ₄ is defined as y ₃ and y ₄ , respectively. ).

Therefore, the ratio of these difference values is obtained, and the x coordinate which gives the inflection point, that is, the boundary coordinate value x 'is determined based on the ratio. In other words, the boundary coordinate value x 'is a large interval (before in this embodiment the coordinates interval (S ₂₎ side) of the rear coordinate interval S ₃ Tonouchi difference value between the coordinates before section S ₂ as a characteristic of the quantization curve Paying attention to the deviation, it can be obtained by the following correction expression x ′ = x ₂ + Δx · [Δy ₂ / (Δy ₁ + Δy ₂ )] (where Δx = x ₃ −x ₂ ). As a result, a coordinate value x ′ that minimizes the quantization error, that is, approaches the inflection point A as much as possible is obtained.

Therefore, according to this embodiment, the occurrence of a quantization error can be suppressed as much as possible by a relatively simple operation, and as a result, the thickness (width) of the barcode and the barcode interval can be detected very accurately. be able to. In this embodiment, the bar code is used for pattern recognition. However, the present invention is not limited to this, and can be applied to the recognition of other patterns such as a color code.

[0012]

As described above, according to the recording signal reading signal processing method of the present invention, the main coordinate section is taken into account by taking into account the ratio of the difference values in the section immediately before and after the main coordinate section. The width from the start point of the section to the boundary coordinate value is determined, and the quantization error is corrected so that the boundary coordinate value shifts forward and backward from the center position of the main coordinate section according to the magnitude of the difference value ratio. Therefore, the generation of a quantization error can be suppressed as much as possible even in a digital system, so that the record slip can be read as accurately as possible.

[Brief description of the drawings]

FIG. 1 is a waveform chart showing a signal processing method when a barcode is read by using the recording signal reading signal processing method according to the present invention.

FIG. 2 is a graph showing a curve of a quantized digital signal used for describing a method of processing a read signal of a record slip according to the present invention.

FIG. 3 is a waveform chart showing a signal processing method using a conventional analog system.

FIG. 4 is a waveform chart showing a signal processing method using a conventional digital method.

[Explanation of symbols]

 2 analog signal 3 (quantized) digital signal

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinichi Kato 1-10-12 Ueno, Taito-ku, Tokyo Japan Electric Seiki Co., Ltd. (58) Field surveyed (Int. Cl. ⁶ , DB name) G06K 7 /Ten

Claims (2)

(57) [Claims] An analog signal output from a reading means for reading a code recorded on a record slip is quantized to a digital signal by an A / D conversion means, and a difference process of the quantized digital signal is performed. A method of processing a read signal of a record sheet for outputting a signal at a coordinate interval according to the code width, wherein when performing a difference process between the quantized digital signals, a main coordinate section giving a maximum difference value The correction is performed according to the value of the ratio between the difference values in the immediately preceding coordinate section and the immediately following coordinate section, and the boundary coordinate value corresponding to the boundary portion of each code is determined. Signal processing method of a record slip to be executed. 2. The difference value between the quantized digital signal in the coordinate section and the post-coordinate section is defined as Δy ₁ , Δy ₂ ,
X is the starting point position coordinate of the main coordinate section, and Δx is the value of the main coordinate section
That when you, read boundary coordinate value x 'following correction equation x' of record file according to claim 1, characterized in that it is determined by = x + Δx · _{[Δy 2 / (Δy 1 + Δy} 2) ] Signal processing method.