LASER

The word 'laser' has become so much a part of our everday vocabulary that we tend to forget it is an acronym derived from the rather long-winded description light amplification by stimulated emission of radiation.

Lasers are often thought of as a new technology but have in fact been in existence longer than many people realise. The theory of lasers was suggested in 1957 and the first laser was built in 1960. Long before that, at the turn of the century, Einstein produced equations which describe the main physical mechanism by which laser action occurs, although this was unbeknown to him at the time.

Many companies and government institutions became imterested in lasers and started developing their own without any specific application in mind. As a resulty lasers became known as 'a solution looking for a problem'. Nowadays lasers are developed for specific tasks and their characteristics are developed to meet the requirements of the application.

Lasers probably have one of the widest range of applications of any type of device, including cutting and welding metals, surgery, data reading and transmission, holography, accurate measurement of physical parameters, non destructive testing, and coding and marking products on the production line.

Laser marking systems came onto the market about 30 years ago. These early systems employed scientific lasers and were not designed to cope with the harsh dusty and wet environments found in many factories. Nor were they designed for continuous operation 24 hour per day, 7 days per week - something we take for granted today.

The initial focus was therefore on 'ruggedising' these systems rather than developing new technology formats to deal with changing market requirements.

How a laser works
All lasers share the same basic principles but are differentiated by the way the products are engineered, by the materials used and by the characteristics of the laser output beam.

Components of a Laser
There are three main components to any laser:
The lasing medium: This can be a gas such as carbon dioxide (CO2), a solid such as Neodymium: Yttrium Aluminium Garnet(Nd:YAG) or a liquid such as a dye.

Benefits of laser coding
In those applications where laser is a suitable coding methodology, it brings with it a number of attractive benefits:
. Indelible codes: Codes are etched into the surface (no unauthorised removal; anti-counterfeiting).
. High quality codes: Some systems can generate near letter qulaity printing.
. Clean codes: no additional materials required, just extraction of by-products generated during the laser marking process.
. Low maintenance: Minimal weekly checks and 4,000 hour service intervals
. Low running costs: Low consumables cost.
. High reliability: With coding q legal requirement in some industries, no coding equals no production so reliability is key. Laser coders are among the most reliable coding and marking devices on the market.
. Non contact: enables high-spedd printing as there is no pyhsical contact with the surface and marking devices on the market.
. Programmability: enables variable information to be printed.

The future
Although laser technology as a whole is moving forward very quickly, the relevance of these advances to coding and marking applications is limited. In other words, Changes are likely to be of an evolutionary rather than a revolutionary nature. Neverrheless, developers of laser marking systems are always in search of improvements in the form of systems which:
. are capable of coding faster and on a wider range of substrates
. are more compact
. cost less to produce.
For users, achievement of these goals will ultimately translate into powerful and flexible systems at a lower price.

Glossary of commen laser terms
CW (Continuous-Wave) laser: The laser emits a beam continuously (compared with the short bursts of a pulsed laser).
Dwell time: The length of time the laser dwells on the substrate to print a dot.
Beam mode: The distribution of energy across a laser beam.

Diagram 8
beam mode


Beam divergence: A measure of how much the radius of a laser beam expands as it travels away from the laser source.

Diagram 9
beam divergence