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Character Verification Checker
8.4
Setting the Process Conditions
Example:
If the Rotation Angle setting is 6° and the Delta Angle setting
is 2° , searching is performed every 2° over the range +/−6° .
(−6° , −4° , −2° , 0° , +2° , +4° , +6° )
Note
When the template is registered, it is a 0° image.
The smaller the Delta Angle setting, the better the detection
accuracy, but processing also takes longer.
Threshold Value
This setting is used to set the difference in gray level for the extraction when comparing
a target object with the registered reference image. Parts for which the difference in gray
value is larger than the threshold are extracted as white pixels.
Note
The gray value comparison is performed on all pixels in the
registered image.
By changing the threshold value it s possible to extract missing
parts only as white pixels, and to extract parts with different
brightness as white pixels.
Registered character
image
Gray value = 200
Background gray
value: 30
− Gray difference between the registered character
and the inspection character = 200 − 140 = 60
− Gray difference between the registered character
missing part and the inspection character = 200 − 30 = 170
Filter
By applying a filter you can compress the differential result and eliminate unwanted
parts. Also, by expanding after compression, and then compressing again, you can
gradually remove unwanted parts without greatly affecting other parts.
Refer to 4.13 File Setup for more details.
8 − 16
Inspection character
Gray value = 140
Threshold value = 100
Threshold value = 30
Background gray
value: 30
OCR Type A230
Extract parts that have a
difference in gray value
of 100 or more (i.e. only
extract the missing part)
Extract parts that have a
difference in gray value
of 30 or more
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