Colour Schemes

The barcode scanner does not see in colour like our eyes but is purely looking for the difference in reflectance between the bars and the background colours. The scanner only sees in red as the laser light is in the red part of the spectrum and is simply looking for the difference in reflection of the light between the bars and the background. The bars are designed to absorb a lot of light and reflect only a little and the spaces are the opposite where they absorb very little and reflect a lot. In essence we are enabling the printed symbol to communicate with the computer via a series of 1’s and 0’s. So you will need to pick your colours carefully, ideally black bars on a white background, however there are some other colours that are suitable for each.

The above are just some examples of some colours that will work and others that will not. A good rough guide is to take a red coloured piece of lighting gel and hold it in front of the colour combination you want to use, if you can’t see it now then nor can the laser scanner. Often colours are chosen because the packaging is already being printed in one of those colours and it will save additional print costs. Be careful that this does not compromise your barcode readability. You will also need to ensure that the colours are used the right way round and that you do not get the negative effect as in the first example in the no read column. If in doubt ask us!

SIZE matters!

Barcodes come in many shapes and sizes, within the retail sector and in particular EAN (European Article Number) codes come in a range of magnification factors that range from 80% through 100% (nominal) to 200% magnification factor. The larger the barcode the bigger the bars and so the greater the range and depth of field the barcode scanner will have. In addition the larger the barcode, the greater the print tolerances available. An example of this is that if you are printing a barcode at 80% magnification you only get a tolerance of plus or minus 30 microns where as at 100% it is plus or minus 100 microns. This is important when you are considering which print process you will be using to produce your labels and onto what substrate. Different print processes are able to work within certain print tolerances so for example offset litho will be able to print onto paper very accurately where as flexographic printing onto plastic bags will not have the same resolution and accuracy but will be required in this combination for production reasons so a larger barcode would be required in these circumstances.

IN addition to the magnification factor of an EAN or UPC code and the physical width of any other barcode you need to consider the height of the bars too. If a barcode is to be read with a hand held laser scanner then as long as the height is 10 mm or so it should make reading easy enough as the laser line has to cover the entire width of the code in one pass to stand a chance of decoding the barcode. If the barcode is to be bread at a couple of metres or more distance then the bars may well benefit from being taller. However if the barcode is to be read by an omni directional scanner (typically point of sale and thus an EAN or UPC code) the full height of the barcode should be maintained where ever possible to ensure a truly omni directional read capability. Truncation can be affected if necessary but it is never recommended to go below 50% of the nominal height for the code. It should be noted that these are general guidelines and each application would perhaps need some detailed analysis to ensure all the parameters are met so please contact us for more information.

These codes will read with the scanner line at angles

These codes will not read

With severe truncation it will make it difficult to read with hand held scanners and almost impossible to read with omni directional scanners

Quiet Zones or Light Margins

The quiet zones or light margins are areas to the immediate left and right of the barcode which need to be kept clear of any colour change, text, boxes or lines to allow for the scanner to rationalise the background reflectance and be able then to determine the reflectance difference for the bars. If this area is infringed the likelihood is that the barcode will not scan easily if at all. The minimum quiet zone should be either 10 times the minimum “x” dimension (smallest bar dimension) or 5 mm which ever is the greater. The EAN system normally has some form of marker to show where this should be. In the main they are in the form of the following tow symbols “<” & “>” although with the EAN-13 code the leading digit is normally used as the left hand indicator.

Check Digits

These are not applicable to all barcode symbologies and are optional on others. The EAN and UPC systems both use a mandatory check digit to ensure where possible that the barcode has been read correctly and decoded and transmitted to the system correctly. In essence it uses a formulation and in the case of EAN and UPC a modulus 10 check digit calculation to arrive at the final digit. There is an automatic check digit calculator that will enable you to calculate your check digit or check the one you have to ensure it is correct. To use it click here.

Location, Location, Location!

This is not just something for people who are looking for a place to live but where you are considering placing a barcode on an item not just from a design and marketing point of view but also from a retail point of sale point of view. You also need to consider the position the code will end up in when the packaging is finally assembled as often seems in plastic wrappers and creases in outer packaging can occur during assembly and make the barcode unreadable. There are a number of basic considerations for positioning the barcode and these are as follows: -

• Keep the code away from edges and corners where it is likely to get damaged
• Avoid areas on packaging where the over wrapping is going to have a seam or wrinkling over the top of the code as this will make it unreadable.
• On cylindrical items have the height of the bars running round the curved surface to that you can avoid having the code disappearing round the cylinder and making it impossible to read the code.
• Avoid having the barcode near to edges in the finished design as during packaging these can move and result in having the barcode running around the corner of a package.
• Avoid areas on the package that could become distorted during the packaging process, as again this will undoubtedly affect the overall readability of the barcode.
• If you are packaging a number of single units with barcodes in a special offer wrapper and perhaps selling a number of single products at a special price and thus the outer wrapping will carry a different barcode ensure the barcodes on the single products are completely obscured to ensure they cannot be read at the point of sale.
• Ensure that the barcode is still readable when the liquid or goods are placed inside the container in particular here we are thinking of clear plastic bottles or translucent ones where the filling can have a marked effect on the read rates.
• Be aware that high gloss and metallic finishes on packaging can cause issues over reading of the barcodes.

Quality control is paramount

Having produced the bar-coded packaging you need to ensure that the barcodes contain the correct information, the check digit is correct and that they are produced within the specification for the symbology and that there is no risk of there being a mis-decode when they are read. The human eye can go some way towards spotting glaringly obvious errors however it cannot judge print errors down to hundredths of millimetre accuracy. In order to do this you will need a verification unit that can scan the barcode and compare the measurements against the industry standards for the symbology and report the results including deviations to the operator. These devices come in many shapes and forms and will vary in price according to the complexity of the device and its reporting capability. Please contact us for more information on these devices