Telecentric is much better for high end application.
Why?

Lens differences

What is the difference between a standard lens and a telecentric one?

The angle between the laser beam and marking surface changes.

  • With the standard lens, the angle goes from 90° at the center of the marking field to 60° in the end of the marking field.
  • With the telecentric lens, the laser beam is always perpendicular to the marking surface.

Marking Area

The standard lens marking area is bigger than the physical size of the lens itself. As the laser beam is sloped, it is possible to obtain different marking fields simply by moving away from the lens. Each focal corresponds to a certain marking area, standard ones are ø140, ø220, ø290, ø420, ø710.

The telecentric lens marking area is equal to the lens diameter minus the diameter of the laser beam that goes through it. This laser beam is usually ø10mm or ø15mm.

Bigger lenses are much more expensive, because the lens diameter has to be the same as the marking field.

Homogeneous focusing

With the FFL lens, the shape and the dimension of the focus point changes, because the angle between the laser beam and the working bench changes its sizes from the center (where it is perpendicular) to the end.

At the center, we will see a perfectly circular focus point and the spot will have a minimum diameter. At the end of the marking area, the shape is extended, considering the intersection between the cylinder and the surface at various angles. This variation determines a power variation.

With the telecentric lens, the beam is always perpendicular, so the focus point is always circular and uniform on the entire surface. The power density is the same everywhere.

ADVANTAGES DISADVANTAGES
STANDARD LENS
  • Reduced costs
  • The working area is bigger than the lens diameter, without a defined limitation
  • Spot dimension and shape change from the center to the end of the marking area
  • Energy density changes from the center to the end of the marking area
  • The marking area changes on the basis of the distance from the lens
TELECENTRIC LENS
  • Spot size invariable
  • Constant energy density
  • Marking sizes don’t change when the distance changes
  • The marking area is equal to the lens diameter minus the diameter of the laser beam plus a safety margin
  • High costs
  • When the marking area increases, the costs increase exponentially

Date: 20/12/2019

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