For those of us who remember the early days of barcode verification, the issue of selecting the correct aperture for the 1D barcode we needed to verify may be an unpleasant memory. Early verifiers like the PSC Quick Check 300’s and 600’s were wand-based, and you needed a collection of different wands of various apertures (at $375 each) to verify barcodes with a range of X dimensions. The range of available wand apertures started at 3 mil for X dimensions from 4 to 7mil, a 5 mil aperture for X dimensions from 7.1 to 13 mil, a 10 mil aperture for X dimension from 13.1 to 25 mil, and a 20 mil aperture for X dimensions of 25.1mil and larger.
The verifier aperture must be smaller the barcode’s X dimension for reasons of verification accuracy. If the aperture is larger than the X dimension, it is difficult if not impossible for the scanner or verifier to locate the edges of the bars and—more to the point—correctly gauge the critical reflective differences between bars and spaces of varying widths.
An aperture excessively smaller than the X dimension is also ill-advised because it increases the likelihood of detecting very small imperfections or reflective differences in the barcode—voids in the bars and spots in the spaces, and falsely exaggerating and downgrading the Defects parameter. While the aperture must be smaller than the X dimension, it must not be too small.
But there is an additional consideration that relates to why verification is being done in the first place. The reason for verification is to predict how the barcode will perform based on how it will be scanned. Barcodes on shipping cartons—those very large GS1 ITF-14 symbols—are scanned with fixed mounted scanners with larger 10 mil apertures. Barcodes on consumer items are scanned with handheld scanners with smaller 6 mil apertures.
If you know where your barcodes are going to be used, it is more accurate to verify those barcodes with the same aperture as the scanner that will ultimately be used to decode it. The ability to set the aperture manually makes it possible to ensure that the verification grade will accurately predict how the barcode will perform in its actual usage.
Recently the GS1 specification for mid-size Code 128 and large ITF-14 barcodes has been updated to reflect these differences. In order to comply with these changes, some verifier manufacturers have modified their software to enable users to make these adjustments. Interestingly, not all verifier manufacturers are able to do this due to the way their software is written.
Here is what the settings look like in Axicon 1D software.
- With the General Distribution setting the verifier will use a 10 mil aperture as required by the aperture settings table in the revised GS1 General Specification.
- With the Hand Scanning setting the verifier will use a 6mil aperture, appropriate for consumer point-of-sale and healthcare scanning.
If neither of the user does not force an aperture by selecting one of these options, the Axicon verifier will automatically select an appropriate aperture based on the width of the X dimension is detects. In all cases, the selected aperture will be reported as required in the standard ISO grade reporting format of
…as shown in this image of an Axicon 1D Verification Report:
The grade for this UPC symbol is 0.0/06/660 indicating and ISO grade of 0.0, using a 6 mil aperture and 660 nm (laser emulating) light. The equivalent ANSI grade is (F).