JP3205289B2 - Dot character inspection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for inspecting dot characters engraved on a vehicle body, for example.

[0002]

2. Description of the Related Art Conventionally, when a dot character is measured with a visual sensor or the like and compared with reference data to judge whether the character is defective or not, the character is determined to be defective due to a trivial difference despite being visually readable. For example, in order to eliminate
A technique such as -138049 is known. In this technique, a dot character to be inspected is read, and the read character is compared with a previously stored normal character pattern or a dot-deleted character pattern obtained by deleting several dots from the normal character pattern, and a predetermined matching rate is obtained. When it is determined to be normal.

[0003]

However, in the case of the above technique, the quality is simply determined by comparing the measured character pattern with a reference character pattern, and factors such as measurement errors are considered. For example, when the measurement error is large, the possibility of erroneous determination is large.

Accordingly, an object of the present invention is to prevent a good character from being erroneously determined to be a bad character when measuring a dot character by a measuring means and comparing the dot character with reference data to judge pass / fail. .

[0005]

In order to achieve the above object, according to the present invention, there is provided a dot character inspection apparatus according to claim 1, wherein a dot display character is measured and compared with reference data to judge pass / fail. In the method, an indefinite area slightly larger than the measurement error is provided at a boundary part of the determination criterion of the determination criterion, and for a character determined to be this undetermined area, re-determination is performed a predetermined number of times by a plurality of character patterns registered in advance. In this case, when it is determined that the area is an indefinite area, the area is visually determined.

Here, when the character is measured by the measuring means and compared with the reference data to determine the quality, it is necessary to consider a measurement error of the measuring means. That is, in order to always determine that a defective character is defective, it is necessary to shift the pass / fail judgment level of the criterion to the defective area by a measurement error. However, when the measurement error increases, it cannot be ignored. In particular, when the measurement error is large, if the pass / fail judgment level is shifted to the defective area side, a situation in which a good character is necessarily determined to be a bad character inevitably occurs.

Therefore, an indeterminate area slightly larger than the measurement error is provided at the boundary between the good area and the bad area based on the determination criterion. Is repeated a predetermined number of times, and if it is still determined to be an indefinite area, it is visually determined to prevent erroneous determination of a good character as a bad character. Here, the dot character may be printed by an ink jet printer or the like, or may be stamped by a dot marking machine. The measuring means may be based on pattern recognition, or may be based on measurement of the number of hit points, position, embossing accuracy, character size, and the like.

According to a second aspect of the present invention, the character judging method according to the first aspect is combined with another character judging method to judge pass / fail.

[0009] If the pass / fail judgment is made by combining a plurality of character judging methods, the accuracy can be further increased.
Here, as a combination of a plurality of character determination methods, for example, in the case of a dot engraved character, a combination of different types such as a determination based on measurement of embossing accuracy and a determination based on measurement of pattern accuracy is effective.

[0010]

Embodiments of the present invention will be described with reference to the accompanying drawings. Here, FIG. 1 is an explanatory diagram showing an example of a determination criterion according to the present invention, FIG. 2 is a flowchart showing an example of a processing flow of measurement data, and FIG. 3 is an example diagram of a combination of a plurality of character determination methods.

The dot character inspection method according to the present invention is applied to a case where dot characters such as a vehicle body number stamped on a vehicle body such as a motorcycle are inspected. In the embodiment, the inspection is performed by an image reading device. The quality is judged by combining the pattern identification and the reading result of the embossing accuracy, and the characteristic part of the present invention is mainly applied to the judgment on the pattern identification side.

That is, for example, AF27-486032
When characters such as are read by the image reading device, for example, 3 and 8
When a character having a similar shape or the like can be read by either of them, the probability of being processed as a defective character increases, and if a character determined to be defective is measured again, it becomes OK. Situations occur. A similar situation occurs when the positions of the dots are slightly shifted.

Accordingly, the present invention provides a method in which an area which cannot be determined by the measuring means is defined as an indefinite area, especially when the reading accuracy is low, and a character determined to be in the undetermined area is a plurality of registered in advance. The re-determination is performed a predetermined number of times based on the character pattern, and if the area is still determined to be indefinite, the area is visually checked to optimize the determination.

That is, for example, when the measuring means is an image reading apparatus and the criterion is the degree of coincidence between the measurement data and the reference data, as shown in FIG. Is ± α%, an indeterminate region (hatched portion) larger than the measurement error is provided, and the upper limit of the indeterminate region is made to coincide with the line of x + α%, so that (x−β%) to (x + α%) Area is defined as an undefined area.

When the degree of coincidence is equal to or more than x + α%, O
If it is determined to be K and x-β% or less, it is determined to be NG,
The influence of the measurement error is eliminated, and there is no inconvenience that a good one is judged as bad or a bad one is judged good.

Further, when it is determined that the area is an undefined area, the matching degree is determined again based on a different registered character pattern.

FIG. 2 summarizes the above-described determination method based on image reading. First, a character is read by the image reading device, the measurement of the degree of coincidence and the measurement of the coordinates of each dot are performed, and if the coordinate value is outside the OK area, it is determined to be NG. If the coordinate value is within the OK area, it is determined whether or not the coincidence is within the OK area (x + α% or more in FIG. 1). If the coincidence is within the OK area, it is determined to be OK. .

When the degree of coincidence is outside the OK area (x + α% or less in FIG. 1), the degree of coincidence is indefinite (x + α% to X in FIG. 1).
−β%), and if it is outside the indefinite region, it is determined to be NG. If it is within the undefined area, re-determination is performed using a different registered character pattern. That is, it is determined whether or not the degree of coincidence is within the OK area by comparing with a different registered character pattern. If the degree of coincidence is within the OK area, it is determined to be OK. If the degree of coincidence is outside the OK area, it is determined whether or not the degree of coincidence is in the indefinite area. If the degree of coincidence is out of the indefinite area, it is determined to be NG. Processing is performed, and such inspection is repeated a predetermined number of times. Then, it is visually confirmed whether or not the area which is finally left as the undefined area is really NG.

By the above-described inspection method, it is possible to reliably prevent a problem that a character is determined to be a bad character, in spite of the fact that the character can be visually identified.

Next, the determination of the stamping accuracy as another determination method used in the present embodiment is performed by comparing with a pin stamping reference created in advance.
For example, reference values such as the number of dots, the depth of embossing, the inclination of embossing, and the position of embossed characters are determined.

In this case, the measured value of the embossing accuracy is indicated by a numerical value. By comparing the measured value with a reference value, it is possible to judge the pass / fail by the numerical value, and in particular, an erroneous judgment caused by a measurement error does not pose a problem. In the embodiment, an indefinite area is not provided, and the area is divided into only an OK area and an NG area.

An example of a combination of the determination result based on the pattern recognition by the image reading apparatus and the determination result based on the stamping accuracy will be described with reference to FIG.

In this example, when one of the determinations is NG, the final determination is NG, and when both are OK, the determination is OK. When the determination result based on the pattern comparison is an indefinite area and the determination result based on the stamping accuracy is OK, the re-determination using a plurality of character patterns is repeated a predetermined number of times, and finally the determination is made visually. I have.

By combining a plurality of determinations as described above, more accurate determinations can be made. Of course, the number of combinations and the like are arbitrary.

The present invention is not limited to the above embodiment. Those having substantially the same configuration as those described in the claims of the present invention and exhibiting the same operation and effect belong to the technical scope of the present invention. For example, the dot character may be other than the engraved character, and the determination target to be applied may be other than the determination based on pattern recognition.

[0026]

As described above, according to the dot character inspection method according to the present invention, an indeterminate area slightly larger than the measurement error is provided at the boundary of the judgment of the criterion. For a character determined as, a re-determination is performed a predetermined number of times using a plurality of character patterns registered in advance, and if it is determined as an undefined area, it is visually determined. Judgment can be prevented. Further, if a plurality of character determination methods are combined to determine the quality, a more accurate determination can be made.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing an example of a determination criterion according to the present invention.

FIG. 2 is a flowchart showing an example of a processing flow of measurement data.

FIG. 3 is an example of a combination of a plurality of character determination methods.

──────────────────────────────────────────────────続 き Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01N 21/88

Claims (2)

(57) [Claims] 1. A dot character inspection method in which a dot-displayed character is measured and the result is compared with reference data to judge whether the character is good or bad. A large undefined area is provided, and for a character determined as the undefined area, re-determination is performed a predetermined number of times using a plurality of character patterns registered in advance. A dot character inspection method characterized in that: 2. A dot character inspection method, wherein the character judgment method according to claim 1 is combined with another character judgment method to judge pass / fail.