Introduction

Barcode quality continues to be a vital aspect of any finished packaging. Every time a barcode fails to scan, costs are incurred. Yet, not everyone who creates and prints barcodes checks the quality of the image during production. It is not difficult to create and print a good quality barcode image but it is also too easy to print a bad one.

Traditionally bar code film masters were made on special photo plotting machines to create extremely accurate images that could be stripped into other packaging artwork and the specialist companies that supplied these film masters would have expensive micro-measuring equipment that was capable of checking the accuracy of the bar code as it was made.

Today most bar code images are created and incorporated into artwork as digital master images and often the bar code quality is not checked until after the final printed packaging is available. Verifying the barcode image that is part of film artwork has often been a difficult process to achieve in practice, even though the benefits of checking the barcode at this stage, prior to producing printing plates, can save time and money.

To address this issue, Axicon has added a special mode of operation to their Apple Macintosh based application that enables verification for bar codes on film. At the pre press stage the data that is encoded in the bar code can be checked but also the dimensional accuracy and whatever allowance that might be built into the image to cater for bar width changes during the imaging process and of course with subsequent ink spread onto the printed surface.

The Axicon Mac based verifier can be used to perform these dimensional checks but the image has to be captured in a different way than it would be when verifying final printed bar code symbols.

The key difference from verifying printed bar codes is that symbols on film should be imaged using light illumination that passes through the film from beneath the bar code. This enables better measuring accuracy than when illuminating from above as with printed symbols.

Specifications

Before we go ahead and get into more detail on how the pre press verifier option works, here is a list of responses to the most frequently asked questions.

• By "Pre Press verifier" we mean a verifier to check barcode film masters and/or film artwork prior to producing printing plates.
• To use the verifier as a pre press verifier, you must use it under the Apple Macintosh environment and check the Transmitted Light Mode (TLM) option in the preference menu. As a result of checking this option, the LEDs will be switched off.
• The film is then placed on top of a light table and the transmitted light going through is used to illuminate the barcode when the scan is taken.
• The transmitted light mode option is a free option of the Mac software and comes included in the standard version of the Mac software (As of version 0.95 of the software). The option is not available on the PC version of the software and we have no plan to include it at the moment.
• All three Axicon series; 6000, 6500 and 7000, with USB connection, can be used for this purpose.
• The verifier can be used either as a printed barcode verifier or a pre press verifier whether you choose to uncheck or check the TLM option. This means that whether an end user purchases a verifier to check printed barcodes or to check film artwork, he will get both options at no extra cost.
• Please note that the Axicon verifier software for Apple Mac will work on version Mac OSX 10.2 and above.
• The verification performed will not give you an ISO 15416 grade because that standard is only applicable to printed symbols.
• The parameters checked as part of the verification of the film are:
  • If the image is negative or positive
  • Light margins, check digit, decoded number, and magnification
  • Bar Width Adjustment. You have the option to enter the expected BWA and the software will check its accuracy.
  • Elements dimensional analysis.
• A verification report specific to the use under the TLM option can be printed.
• Please note also that when using the verifier in TLM a dedicated transmitted light calibration has to be performed. (More about this below.)

The “Transmitted Light” Mode

In order to use the Axicon verifiers for film it is therefore necessary to extinguish the normal LED illumination and place the verifier onto film which is itself sat on a light table or light panel and the software is then set to the transmitted light mode setting for subsequent scans. There is an important installation procedure to be performed prior to any measurements being made, however, as the verifier itself has a fixed exposure that is configured during manufacture for printed symbol illumination and it is therefore necessary to match the transmitted light level to give roughly the same amount of collected light at the verifier.

It is most likely that the light level required is less than a standard light table or light panel would give, so the light level will need to be reduced. Filter material can be used, perhaps just in one particular location on the light table or if the brightness of the illumination can be adjusted then this might be a simpler option. It is important that the illumination remains consistent and within a certain range and a calibration process (independent of any normal calibration for printed symbols) is used in order to check that the light level is within the correct range.

Configuring and Calibrating in Transmitted Light Mode

The verifier application is configured for analyzing film artwork from the preferences screen by checking the transmitted light mode check box.

It is also possible to enter a target bar width adjustment (BWA), which is usually a bar width reduction (BWR) and therefore a negative value in this box. When a bar code is then scanned in this mode the actual measured bar width adjustment will be measured against the target that was expected.

Analyzing Bar Codes on Film Artwork

If a negative bar code image is detected then this is reported on the main screen in the yellow box seen. Note that final printed bar code symbols must never be negative images and in printed symbol mode such an image would be highlighted with a red box.

Printed Reports