JPH0668240A - Character inspection device and character inspection method - Google Patents

Abstract

PURPOSE:To reduce an erroneous judgement at the time of the judgement of the quality of a character printed on an article. CONSTITUTION:The character to be inspected printed on a video cassette VC is photographed by video cameras 11A-11E, and inspected character picture signals are obtained. And also, reference character picture signals preliminarily written in the reference character information memories of picture processing parts 19A-19E are read, and compared with the inspected character picture signals. Then, when the quality of the character to be inspected is rejected from the compared result, the alignment start position of the inspected character picture signals with the reference character picture signals is changed, and the inspected character picture signals are compared with the reference character picture signals again. Then, when the number of time of re-comparison is set, the alignment start position is changed each time the re-comparison is operated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a character inspection device and a character inspection method for inspecting the quality of characters printed on an article.

[0002]

2. Description of the Related Art Conventionally, pad printing, which is one type of printing, has been used in various fields. This pad printing is
Imprint the printing ink on the block engraved with the shape of the letters,
The printing ink is attached to a pad made of rubber, and the pad is pressed onto an article for printing.

In this pad printing, there is a problem that the print quality is likely to change depending on the condition of the printing machine. Therefore, an attempt has been made to inspect printed characters. This test is
After the inspection object characters printed on the object to be printed (for example, the case of a video cassette) are photographed by a TV camera, and the inspection character image signal based on the photographing is temporarily stored in the memory,
The inspection character image signal stored in this memory is compared with the reference character image signal read from the reference character information memory. Then, in this comparison, if the correlation coefficient of each part of the inspection character with respect to the reference character is higher than a certain level, it is determined as pass, and if it is less than that, it is determined as fail.

[0004]

By the way, in the above-mentioned conventional character inspection method, when the alignment with the reference character is not accurately performed, even if it is close to the pass, it is judged as fail. There was a problem that it would end up.

That is, in the conventional character inspection method, since high speed is required, the target area for alignment is 7 × 7 centered on the alignment start position (cutout position).
Since it is limited to pixels, the accuracy is lower than the method of squeezing around the cutout position. For this reason, depending on the cut-out position, there may be a case where the best match with the reference character is missed, and even if it is close to passing, it will be judged as failing.

Further, particularly in pad printing, as described above, the detailed shape of characters printed according to the state of the printing machine,
Since the density and the like change subtly, and the change also changes depending on the day or the difference between morning and afternoon, the accuracy of the pass / fail judgment further decreases.

Therefore, an object of the present invention is to provide a character inspection apparatus and a character inspection method capable of reducing erroneous determinations due to misalignment.

[0008]

In order to achieve the above object, a character inspection apparatus according to a first aspect of the present invention captures a character to be inspected printed on a storage means in which a reference character image signal is written. A comparison determination for comparing the reference character image signal with the reference character image signal and the inspection character image signal corresponding to the inspection target character obtained by the imaging unit, and determining the quality of the inspection target character from the comparison result. And a re-inspection unit that inspects the inspection target character again when the comparison determination unit determines that the inspection target character is unacceptable.

According to a second aspect of the present invention, there is provided a character inspection device having a re-inspection number designating unit capable of arbitrarily setting the number of re-inspections in addition to the structure of the character inspection device according to the first aspect. The re-inspection means re-inspects the inspection target character the number of times set by the re-inspection number designating means.

A character inspection apparatus according to a third aspect of the present invention is the character inspection apparatus according to the first or second aspect of the present invention, wherein the reinspection means performs the inspection when starting the reinspection. It is characterized in that a start position of alignment between the character image signal and the reference character image signal is changed.

In the character inspection method according to the present invention, the inspection character image signal obtained by photographing the inspection object character printed on the article is compared with the reference character image signal read from the reference character information storage means. In the character inspection method for determining the quality of the inspection target character, the quality of the inspection target character is determined to be unacceptable, and then the inspection target character is compared again.

[0012]

According to the first aspect of the invention, the inspection character image signal obtained by photographing the inspection target character printed on the article is:
It is compared with the reference character image signal read from the reference character information memory, and the quality of the character to be inspected is judged from the result. And if it fails in this judgment,
The quality of the character to be inspected is again inspected. Therefore, even if the initial judgment fails, the re-examination reduces false judgments.

According to the second aspect of the invention, the reinspection in the first aspect of the invention is performed the number of times set arbitrarily. Therefore, the number of erroneous determinations is further reduced as compared with the case where the retest is performed only once.

According to the third aspect of the invention, in the reinspection according to the invention of either the first aspect or the second aspect, the start position for starting the alignment is changed.
Then, the inspection character image signal and the reference character image signal are compared at the changed alignment start position. Therefore, by increasing the number of re-examinations and changing the start position many times, it becomes possible to perform the alignment at the position most suitable for the reference character and further reduce the erroneous determination.

According to the fourth aspect of the invention, similarly to the operation of the first aspect of the invention, the inspection character image signal obtained by photographing the inspection object character printed on the article is stored in the reference character information memory. It is compared with the read reference character image signal, and the quality of the inspection object character is judged from the result. Then, if the result of this determination is unsuccessful, the inspection character image signal and the reference character image signal are compared again.

Therefore, even if the initial judgment is unsuccessful, erroneous judgment is reduced by conducting the inspection again.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Structure FIG. 1 is a perspective view showing the external appearance of an embodiment of a character inspection apparatus according to the present invention. This character inspection device is for inspecting the quality of the characters printed on the pad on the video cassette.
As shown in the figure, it comprises an image processing system 1 and a video cassette transport system 2.

In this figure, the transfer system 2 transfers a video cassette (not shown) that is being transferred, to a belt conveyor 3.
Are sequentially sent to the stages 4A to 4E, and the stage 4E is provided with the sorting device 5, and sorts the video cassettes based on the pass / fail of the print quality determined by the image processing system 1. That is, if the print quality is unacceptable (defective cassette), it is removed from the product line (released to the front side of the drawing), and if it is acceptable (good cassette).
Is conveyed to the next process on the belt conveyor 6.

The sequencer 7 controls the operations of the belt conveyors 3 and 6, the sorting device 5, and the devices and equipment related to these devices in the transport system 2. The sequencer 7 also outputs an image capture signal to the image processing system 1 when the video cassette reaches the stages 4B and 4C.

On the other hand, the image processing system 1 has a stage 4
Milky white acrylic plates 9 installed separately on B and 4C
And two fluorescent lamps 10A, 10B which are installed close to the acrylic plate 9 and parallel to the traveling direction of the biode cassette.
The image processing unit 12 includes five video cameras 11A to 11E, which are installed close to each other on the fluorescent lamps 10A and 10B so as to be linear with the moving direction of the video cassette.

In the acrylic plate 9, two narrow holes h ₁ and h ₂ extending in the moving direction of the video cassette are formed separately. Each of the video cameras 11A~11C are part of the visual field are installed so as to fall within the holes h _1, a video camera 11D, each of 11E, a portion of the field of view in the hole h ₂ It is installed to enter.

In this case, the video cameras 11A to 11C capture images of the printed characters in the inspection area of the video cassette, and the video cameras 11D and 11E capture blank areas on both sides of the inspection area. Take a picture of.

The shooting is performed with the biode cassette stopped. In addition, the acrylic plate 9 is attached to the fluorescent lamp 1.
By placing it between 0A and 10B and the video cassette, it is possible to prevent irregular reflection due to minute irregularities on the surface of the inspection area, and to capture a clean image. Further, as the video cameras 11A to 11C, those using CCD are suitable. The characters include kanji, katakana, hiragana, various alphabets, symbols and figures.

Here, there are the following items as character inspection items. a) Missing characters (broken line, faintness) For example, the bottom part of "u" is worn off or there is no "i" dot. b) Character bleeding For example, the upper half circle of "e" is filled with ink. c) Printing misalignment It depends on the video cassette, but if there is a misalignment of about 3 mm or more to the left and right, it is considered a defective cassette. d) Ink stain Detects stains of about 1 mm ² or more.

FIG. 2 is a front view showing the video cassette VC, and an inspection area DA (16 mm × 180 mm) on the tape pull-out side (the side indicated by arrow A) of the case body.
Characters are printed by pad printing on.

Next, FIG. 3 is a block diagram of the character inspection apparatus. In this figure, 15 CPUs (central processing unit) have RAM and ROM inside. A program (inspection program) for controlling the CPU is written in the ROM. According to this program, the CPU controls each part of the apparatus via the bus (for example, VME bus) B, and the inspection image and the reference image. The calculation of the normalized correlation with the image and the pass / fail judgment are performed. The RAM is used in the operation of this CPU.

Reference numeral 16 is a floppy disk control unit,
The disk drive device 17 is controlled. The floppy disk controller 16 is connected to the bus B. Reference numeral 18 is a floppy disk (3.5 inch type in this figure) in which an image signal of a reference character is written. By inserting the floppy disk 18 into the disk drive device 17, the image signal of the reference character is read out according to a command from the CPU 1.

The image signal of the reference character read from the floppy disk 18 is supplied via the bus B to the image processing units 19A to 19E constituting the image processing system 12. In this case, the image processing units 19A to 19E are provided with a reference character information memory (not shown), and the image signal of the reference character is written in the reference character information memory.

In addition to the reference character information memory, each of the image processing units 19A to 19E is also provided with an inspection character information memory for storing an inspection character image signal, which is photographed by the video cameras 11A to 11E. The inspection character image signal is written. In addition, each of the image processing units 19A to 19E operates by a dedicated assembler program, and executes various image processing techniques at high speed. In addition, these image processing units 1
Each of 9A to 19E is connected to the bus B.

Reference numeral 20 denotes an I / O port, which is a sequencer 7
An image input signal, an inspection determination result, and the like are exchanged between the CPU 15 and the CPU 15. Also, the output of the trackball 21 is input and supplied to the CPU 15. The trackball 21 is used for menu selection of the inspection program.

Reference numeral 22 denotes an operation panel composed of a plurality of switches, a display control circuit (not shown), etc., which is connected to the bus B. The operation panel 22 includes image processing units 19A to 19A.
E and monitor receivers 23A and 23B are connected.

Among the above-mentioned various switches, a re-inspection number designating switch 24 is included. The re-inspection number designating switch 24 is for designating the number of times of character quality inspection, and the character quality inspection is performed only the number of times corresponding to the set value. For example, if it is set to 2 times, the inspection is performed up to 3 times for each character. If it is set to off, re-inspection is not performed.

The floppy disk 18 corresponds to a storage means. Further, each of the video cameras 11A to 11E corresponds to a photographing means. In addition, the image processing unit 11A
11E and the CPU 15 constitute the comparison / determination means 100. Further, the CPU 15 has a function of a reinspection unit. The reinspection number designating switch 24 corresponds to reinspection number designating means.

[0034] Operation will now be described with reference respectively to FIGS operation by the above configuration. FIG. 4 is a flow chart for explaining the character inspection operation. First, in step S1, the reference image is read. That is, the CPU 15 instructs the floppy disk controller 16 to read the reference character image signal from the floppy disk 18.
When the reference character image signal is read from the floppy disk 18 according to this instruction, the CPU 15 supplies this reference character image signal to each of the image processing units 19A to 19E via the bus B and writes it in each reference character information memory.

After this processing is completed, inspection parameters are set in step S2. That is, the CPU 15 displays the menu on the screen of the monitor receiver 23A or the monitor receiver 23B, and allows the user to select this menu to set the inspection parameters. At this time, the menu is selected by operating the trackball 21. Further, the number of re-inspections is set together with the setting of the inspection parameters. This setting is the re-inspection number designating switch 24
Will be held in. After these settings are made, step S
Go to 3.

In step S3, the image capture signal is received. That is, the CPU 15 captures the image capture signal output from the sequencer 7. In this case, the sequencer 7 uses the video cassette VC in the stage 4
An image capture signal is output at the time when the image data reaches B and 4C.

After the image capture signal is received, the image is captured in step S4. That is,
The CPU 15 instructs the image processing units 19A to 19E to write the inspection character image signal corresponding to the inspection character enlarged and photographed by the video cameras 11A to 11E into each inspection character information memory. As a result, each of the image processing units 19A to 19E writes the inspection character image signal in its own inspection character information memory.

Next, in step S5, characters are cut out. That is, the characters of the inspection character image signal written in the inspection character information memories of the image processing units 19A to 19E are cut out. The alignment of the characters is performed by the image processing units 19A to 19E. Here, the reason for cutting out the character is that the position of the character printed in the inspection area varies from video cassette VC to video cassette VC, and is performed to detect that position.

Specifically, in FIG. 5, the image processing unit 1
A horizontal profile of the entire inspection image is created from the stored contents of the inspection character information memories 9A to 19E, and the character string is extracted. Then, a rectangle circumscribing the character is created by the profile in the horizontal direction and the profile in the vertical direction, and the coordinates at the upper left of the drawing are detected. These coordinates are the cutout position of the character.

After the characters are cut out, step S
At 6, the characters are aligned. That is, each of the image processing units 19A to 19E aligns, for each character, the inspection character image signal obtained by cutting out the character and the reference character image signal written in the reference character information memory.

At the final stage of the inspection, the normalized correlation is calculated for each character corresponding to the inspection character and the reference character. At that time, a part of the cut out inspection character is missing. In such a case, the position where the inspection character is simply cut out is not always the most suitable position for the reference character.
Therefore, it is necessary to calculate the normalized correlation in a place where the shapes of the inspection character and the reference character are as close as possible to each other. Therefore, this character is aligned.

The alignment method is performed by calculating the normalized correlation of the horizontal and vertical profiles between the inspection character and the reference character, and detecting where the correlation value has the maximum value.
As a result, the alignment can be performed without being affected by the fluctuation of the illumination and the blur. That is, as shown in FIG. 6, the cut-out position (coordinates) of the inspection character (“a” in this figure)
And the normalized correlations in the eight neighborhoods are calculated, and the direction in which the correlation value increases is detected depending on the magnitude of the correlation value. Then, the five normalized correlations adjacent to the _first pixel P ₁ are calculated, and then the normalized correlations at three points adjacent to the _second pixel P ₂ are calculated.

As a result, the position of the second pixel P ₂ is detected as the place of the maximum value. Note that M_W in FIG.
X and M_WY indicate the horizontal and vertical sizes of the inspection character and the reference character.

After the character alignment processing is completed, a character division inspection is performed in step S7. That is, each of the image processing units 19A to 19E divides the inspection character and the reference character into a normalization calculation, and compares the result with the set reference value. In this case, if the entire inspection character is compared with the entire reference character at once, if the inspection character has a partial defect or a small defective portion such as bleeding, it becomes difficult to determine these. Therefore, the division inspection is performed so that these defective portions are significantly reflected in the correlation value.

Specifically, as shown in FIG. 7, for example, an "S" check character is divided into five areas including the background, and these areas and the respective areas corresponding to the "S" reference character are divided. Compute the normalized correlation between. If even one of the five check character areas has a correlation value smaller than the set reference value, it is determined as a defective character. In this case, as the setting reference value, a different value is set for each area according to the ratio of the characters and the background in the area.

When the character division inspection process is completed, the flow advances to step S8 to determine whether the character is a non-defective character. That is, the CPU 15 determines whether or not the inspection character image signal is a non-defective product, and if it is determined to be a non-defective product, the process proceeds to step S9, and if it is determined to be a defective product, the process proceeds to step S10.

In step S9, it is determined whether the inspection of all the characters has been completed. That is, the CPU 15
Determines whether or not the inspection of all the inspection character image signals in charge of the image processing units 19A to 19E is completed, and if it is determined that the inspection is completed, the process proceeds to step S11 to output the determination signal. This determination signal is supplied to the sequencer 7 via the I / O port 20. As a result, the sequencer 7 carries the next video cassette VC to the inspection position. After outputting the determination signal, the process returns to step S3. On the other hand, if it is determined that the inspection of all the inspection character image signals is not completed, the process returns to step S6.

On the other hand, when it is determined in step S8 that the product is defective and the process proceeds to step S10, it is determined whether reinspection is designated. In this case, CP
If the U15 determines that the reinspection is designated based on the setting value of the reinspection number designating switch 24, the step S1 is performed.
When it is determined that the reinspection is not designated in step 2, the process proceeds to step S11.

In step S12, it is determined whether or not the re-inspection has reached the specified number of times. If it is determined that the specified number of times has not been reached, the process proceeds to step S13, and if it is determined that the specified number of times has been reached, the process returns to step S11. .

In step S13, the position where alignment is started is changed. Then, again, the characters are aligned in step S6, and the division inspection is further performed in step S7.

The change of the alignment start position is performed as follows. First, the position determined by the normal first alignment (this is called P _b ) and the cut-out position extracted by the character cutting process of step S5 (this is called P _a )
If P _b is in the increasing direction than P _a , it is determined that there is a place that best matches the reference character in the decreasing direction, and the position is determined in the first re-inspection. A position where the alignment start position is shifted by one pixel in the decreasing direction from P _a is set.

Then, in the second re-inspection, the position is set to a position shifted by one pixel from P _{a in} the direction opposite to the direction shifted in the first time. Such a process applies to both x and y directions. The change of the alignment start position is performed by each of the image processing units 19A to 19E. With such a re-inspection function, erroneous determination due to alignment failure hardly occurs.

In the above embodiment, the video cassette is stopped and the image is captured, but the image may be captured while the video cassette is moved.

Further, in the above embodiment, the replacement of all characters in the video cassette is performed, for example, every 20 characters, but the value is not limited to this value, and 50 characters, 100 characters are replaced.
It may be performed every 300, 500 pieces.

In the above embodiment, the video cassette is used as the article on which the characters to be inspected are printed, but the invention is not limited to this, and various printable articles are possible. For example: ・ 8mm cassette pad print character inspection ・ Floppy disk screen print character inspection ・ Cassette wrap film misalignment ・ Serial number reading ・ Different product mixture inspection

The printing method is not limited to pad printing, and various printing methods are possible.

[0057]

According to the present invention, it is possible to reduce erroneous determinations due to misalignment, and it is possible to improve inspection reliability and product quality.

[Brief description of drawings]

FIG. 1 is a plan view showing the appearance of an embodiment of a character inspection device according to the present invention.

FIG. 2 is a plan view showing an inspection area of a video cassette.

FIG. 3 is a block diagram showing a configuration of an embodiment of a character inspection device according to the present invention.

FIG. 4 is a flowchart showing a character inspection process of the character inspection apparatus of the embodiment.

FIG. 5 is a diagram for explaining character cutout in the character inspection apparatus of the embodiment.

FIG. 6 is a diagram illustrating alignment of characters in the character inspection device according to the embodiment.

FIG. 7 is a diagram illustrating division of characters in the character inspection device of the embodiment.

[Explanation of symbols]

 7 Sequencer 11A-11E Video Camera (Photographing Means) 15 CPU (Re-Inspection Means) 16 Floppy Disk Control Unit 17 Disk Drive Device 18 Floppy Disk (Storage Means) 19A-19E Image Processing Unit 20 I / O Port 21 Trackball 22 Control Panels 23A and 23B Monitor receiver 24 Re-inspection number designating switch (re-inspection number designating unit) 100 Comparison judging unit VC video cassette

Claims (4)

[Claims] 1. A storage means in which a reference character image signal is written, a photographing means for photographing an inspection target character printed on an article, the reference character image signal and the inspection target character obtained by the photographing means. In a character inspection device comprising: a comparison determination unit that determines whether the quality of the inspection target character is acceptable or not from the comparison result while comparing the inspection target character image signal corresponding to A character inspection apparatus comprising reinspection means for inspecting the character to be inspected again when it is determined to be unacceptable. 2. A re-inspection number designating unit capable of arbitrarily setting the number of re-inspection, wherein the re-inspecting unit re-inspects the inspection object character by the number of times set by the re-inspection number designating unit. The character inspection device according to claim 1, wherein 3. The re-inspection means changes the start position of alignment between the inspection character image signal and the reference character image signal when starting the re-inspection. 2. The character inspection device according to any one of items. 4. An inspection character image signal obtained by photographing an inspection target character printed on an article is compared with a reference character image signal read from a reference character information storage means to determine whether the quality of the inspection target character is acceptable or not. In the character inspection method for determining, the character inspection method is characterized in that after the quality of the inspection target character is determined to be unacceptable, the inspection target character is compared again.