JP3128056B2 - Mark reader - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mark reading apparatus for reading a printed mark with an optical sensor, and more particularly, to a mark which is printed on a medium such as a postal matter whose background color cannot be specified. The present invention relates to a mark reading device that has a large variation and is difficult to recognize.

[0002]

2. Description of the Related Art In a mark reading apparatus, an optical signal from a mark is converted into an electric signal by a photoelectric conversion element or the like, and the voltage is compared with a threshold value to determine whether the voltage is higher than the threshold value. Is determined. In a conventional mark detection method, for example, as described in Japanese Patent Application Laid-Open No. 55-99677, a method of detecting a mark using a plurality of thresholds uses two thresholds. There is a method in which a mark is detected for each value, and if the obtained result is the same, the result is adopted as a result, and if the obtained result is different, determination is impossible. In the above detection method, since the entire detection medium is detected at a certain threshold value, in the case of a mark printed on a medium such as a postal matter in which the background cannot be specified, the output varies depending on the background color (address writing, etc.). Therefore, there is a problem that an undetectable portion occurs.

[0003]

The output of ink (hereinafter abbreviated as ink) which has been conventionally excited by infrared light and emits light in the infrared wavelength range varies depending on the background color. For this reason, when the entire multi-valued image obtained from the image reading device is determined based on a predetermined threshold value and the output change amount, a portion where the mark shape cannot be recognized occurs. In particular, the output of a character written with a writing instrument having a high carbon content or a printed matter is significantly reduced. As a result, there is a high possibility that the output of a postal matter whose background color cannot be specified is reduced. FIG. 2 is a diagram showing a print diagram of a 4-state barcode with a base character, a main scan line output diagram, and a coordinate image diagram of threshold values S1 and S2. Here, a white rectangle is a barcode, and a black character is a character described on a background. FIG. 2B shows an image output in the main scanning direction at the position 101 in FIG. 2A. FIG. 2 (b)
As is clear from FIG. 7, the output is extremely different between the plain portion 102 and the portion 103 where the characters overlap. As a result, when the bar code of FIG. 2A is output using the threshold value S1, the result is as shown in FIG. 2C. When the bar code of FIG. 2A is output using the threshold value S2 smaller than S1, FIG. As shown in d). As shown at 104 in FIG. 2C, the code output of the portion overlapping the character is detected in a shape different from the actually printed mark. In order to recognize the position of the bar where the characters overlap, it is necessary to set the threshold value to the threshold value S2 in FIG. However, in this case, the ink bleeding portion 105 between the marks shown in FIG.
Since the output of the ink splatter 106 during printing is almost the same as the output reduced portion, there is a problem that the output is erroneously detected as a mark, and it is difficult to detect the output reduced portion. SUMMARY OF THE INVENTION An object of the present invention is to solve such a conventional problem and to detect a portion where output is lowered due to a background without detecting noise or a blurred portion of ink, thereby improving a recognition rate. An object of the present invention is to provide a mark reading device.

[0004]

In order to achieve the above object, a mark reading apparatus according to the present invention provides a mark reading device for detecting the presence or absence of a mark.
By using a plurality of different values according to the output level of the sensor and the sensor, a mark with a low output is detected without being affected by a blurred portion of printing, noise, or the like. The output of the ink has a high threshold value (S
If the amount of change is detected in 1), no printing bleeding or ink splattering will be visible as shown in FIG. In the present invention, by paying attention to this, 109 (FIG. 3B), which is an area (width, height) with a mark, is specified in advance with a high threshold value, and only the inside of the area is set to a low threshold value. By detecting using S2, it is possible to detect the position of the mark even in a portion where the output is reduced due to the background.

[0005]

In the present invention, the difference in the output characteristics of the ink depending on the base is absorbed by using two thresholds in one detection. One is a noise removal threshold set to a relatively high level, and the other is an output reduction portion detection threshold set to a low level. In the present invention, by combining these, it is possible to detect the output reduction portion. This makes it possible to detect a portion where the output is reduced due to the background without detecting noise or a blurred portion of the ink, thereby improving the recognition rate.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, taking as an example the detection of a bar code which is a kind of mark.
FIG. 1 is a configuration diagram of a barcode reader according to an embodiment of the present invention. The mark reading device of the present invention is composed of two blocks including an image reading unit 12 and an image recognition unit 13. The image reading unit 12 irradiates infrared light from the light source 2 to the mail 1 running on the transport path, magnifies the reflected light from the printed barcode with the lens 3, and receives the light with the sensor 4 including a plurality of photodiodes. . The output of the photodiode is amplified by the amplifier 5 and converted into a digital signal by the AD converter 6. The converted signal is passed to the image recognition unit 13, synchronized by the latch circuit 7, and stored in the image memory 8 as a multi-valued image. The stored image is transferred to the main memory 10 by the CPU 9 via the general-purpose bus, and the CPU 9 processes and codes the image according to a recognition program also stored in the main memory 10. The coded data is passed to a higher order via a serial interface (serial driver) 11. In the present invention, when the CPU 9 processes an image, a plurality of different values are used according to the state of the background on which the mark is printed and the output level of the sensor as the threshold value for detecting the presence or absence of the mark. Thus, a low output mark can be detected without being affected by a blurred portion of printing, noise, or the like.

[0007] The pre-processing of the barcode coding according to the present invention will be described below by taking as an example the case where the medium is mail. FIG. 2A is a printing diagram of a 4-state barcode with a base character, FIG. 2B is an output diagram of a main scanning line in FIG. 2A, and FIG. 2C is FIG. 2B. FIG. 2D is a coordinate image diagram of the threshold value S2. As described above, in the coordinate image detected at the threshold value S1, 104 in FIG.
As shown by, a bar code overlapping a character cannot be detected. On the other hand, in the coordinate image detected at the threshold value S2,
As shown by 105 and 106 in FIG. 2D, a bleeding portion between the marks and a scattered portion of the ink are detected, and an accurate barcode cannot be detected. Therefore, in this embodiment, in order to detect a mark having a low read output and difficult to recognize, a low level output is detected without being affected by noise by using two different threshold values S1 and S2. I do.

FIG. 3A shows a coordinate image rectangle detection output, and FIG. 3B shows a coordinate image bar width detection output.
FIG. 3C shows a coordinate image bar position specifying output, and FIG.
Is a bar specific position cutout image output. In this embodiment, the outer shape 107 of the entire mark shown in FIG. 3A and the width 108 of each mark shown in FIG. 3B are specified from the coordinate table 1 detected at the threshold value S1 which is not affected by noise. Then, a mark print area 109 is created. This area 1
9 is checked with a threshold value S2 that can detect even a low output, the image of FIG. 3C is output, and a coordinate table 2 is created from this. A mark as shown in FIG. 3D is output from the coordinate table 2 and is coded.

FIG. 4 is a flowchart of a mark reading operation according to an embodiment of the present invention, and FIG. 5 is a format diagram of the coordinate tables 1 and 2 used in the present invention.
The processing procedure of the present invention will be described with reference to FIG. 4 while referring to FIG. 2, FIG. 3, and FIG. 1) First, a multi-valued image is checked using the threshold value S1 in the direction of the arrow (main scanning direction) indicated by 101 in FIG. 2A, and an output is output above the threshold value S1 shown in FIG. The first change point that has risen is the start point of the bar, and the last change point that has fallen is the end point (steps 41 and 4 in FIG. 4).
2). In FIG. 2B, reference numeral 102 denotes a solid output, 10
Reference numeral 3 denotes an output of a character overlapping portion. 2) Next, the above check 1) is sequentially repeated from the left end in the sub-scanning direction to create a coordinate table 1 for the start point and the end point (step 43 in FIG. 4). An image connecting the start point and the end point is shown in FIG. When detected at the threshold value S1, the shape is different from the actual mark, as indicated by 104 in FIG. 2C. If the last line is detected, the process proceeds to the next step (step 44 in FIG. 4). The start point and end point coordinate table 1 has a format and contents as shown in FIG. Coordinate table 2 described later
Are the same as those in the coordinate table 1. In the coordinate table, start point coordinates, end point coordinates (the number of pixels in the main scanning direction), and line positions (the number of pixels in the sub-scanning direction) of the lines constituting the bar are arranged in the order of the sub-scanning direction. Here, the description from the start point 1 and end point 1 of the first bar to the start point 5 and end point 5 of the second bar is shown in FIG. Here, 2
Although only the first one is stored, in the case of FIG.
The data is stored up to the start point 5 and the end point 5 of the seventh bar.

3) Next, the rectangular area of the entire bar code as indicated by 107 in FIG. 3A is specified from the coordinate table 1 created in 2) from the maximum bar length and the outermost bar coordinates (FIG. 3A). Step 45). Here, the outermost bar coordinates are
This is the position of the start and end lines generated first and last when viewed from the sub-scanning direction shown in FIG. 2A, that is, the positions (coordinates) of the outer lines of the bars at both ends in FIG. 3A. 4) Next, from the coordinate table 1 created in the above 2), 108 of FIG. 3B, which is the effective width of each bar, is specified (FIG. 4).
Step 46). At this time, when the bar width is smaller than the original bar width, the bar width at the time of printing is set as the area width. 5) Next, from the rectangular area created in 3) and the bar width specified in 4), a detection area 109 shown in FIG. 3C is specified (step 47 in FIG. 4). 6) Next, in the same manner as in 1), the area specified in 5) is checked with the threshold value S2 shown in FIG. 2B (step 48 in FIG. 4), and FIG. (Step 4 in FIG. 4)
9). Then, when the last area is detected (step 50 in FIG. 4), coding is performed using the coordinate table 2 (step 51 in FIG. 4).

By using the coordinate table 2 created according to the present embodiment for a portion where characters overlap each other, the bar does not affect ink bleeding or noise and the bar can be detected. Become. In this embodiment, the method of creating bar coordinates from the output change point of the multi-valued image and detecting the position has been described. In addition to this, the output is sliced by the threshold values of S1 and S2 to obtain a binary value. It is also effective to create a coded image, specify an area from the binarized image of S1 in the same manner as in the present embodiment, and cut out only a specific area from the binarized image of S2 to obtain a coded image. In the present embodiment, in particular, the threshold value for detecting a mark printed with ink containing a phosphor that is excited by infrared light and emits light in the infrared wavelength region is determined according to the state of the base on which the mark is printed. By using a plurality of different values, the presence or absence of a low output mark can be read without being affected by noise.

[0012]

As described above, according to the present invention,
Since multiple types of thresholds are used to detect the position for mark recognition, it is possible to detect the output reduction part due to the background without being affected by noise or ink bleeding. Improvement can be achieved.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a barcode reader to which the present invention is applied.

FIG. 2 is a diagram of a 4-state barcode print with a base character, a main scan line output diagram, a diagram of a coordinate image of a threshold value S1, and a diagram of a coordinate image of a threshold value S2.

FIG. 3 is a diagram illustrating a coordinate image rectangle detection diagram, a coordinate image bar width detection diagram, a coordinate image bar position specification diagram, and a bar specific position cutout image according to the present invention.

FIG. 4 is an operation flowchart of the mark reading apparatus according to the embodiment of the present invention.

FIG. 5 is a format diagram of coordinate tables 1 and 2 used in the present invention.

[Explanation of Signs] 1 ... mail, 2 ... light source, 3 ... lens, 4 ... sensor,
5 ··· Amplifier, 6 ··· AD converter, 7 ··· Latch circuit, 8 ·
..Image memory, 9 CPU, 10 main memory, 11
Serial driver, 12: Image reading unit, 13: Image recognition unit, 101: Main scanning direction output detection line, 10
2 ... plain output, 103 ... character overlap output, 104 ...
Character overlap image, 105: ink bleeding detection position, 106: print jumping position, 107: barcode rectangle, 108: bar width, 109: bar detection area.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Yoshinari Aoshima 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-62-157978 (JP, A) JP-A Heisei 6-274677 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G06K 7/10 G06K 7/00

Claims (1)

(57) [Claims] 1. A mark reading device for reading a printed mark with an optical sensor, wherein a plurality of different thresholds for detecting the presence / absence of the mark are used according to the state of the background on which the mark is printed and the output level of the sensor. using the value, without being affected by such as printing of bleeding parts and noise, to detect the marks of the low output
That includes an image recognition unit, by the image recognition unit, not affected by noise levels
Identify mark position in scanned image with high threshold
After that, a low level threshold for the specified position
A mark reading device for reading presence or absence of a mark by using