BE12 Zoom Beam Expander


IntroductionBeam Expander
Model BEZ12 zoom beamexpander is designed for use with CO2 lasers having up to 10mm full beam
diameter and 600W CW power.
A zoom beamexpander may be used in conjunction with a focusing lens to produce a variable spot
size at the focus by changing the diameter and divergence of the beam entering the focusing lens.
This facility enables the optimum trade-off between focused energy density and depth-of-focus to
be established for a laser process.
A typical application might be in a long, variable-path system where the input laser beam diameter
is relatively small.
Technical specifications
Dimensions : see Figure 24.121.
Weight : 1.8 kg.
Cooling : Air cooled
Focus range : Afocal (factory set).
Zoom range : x1.0 to x3.5 continuously variable.
Output clear aperture : 46mm diameter.
Input clear aperture : 21mm, 13.1mm usable at M = x3.5.
Beam compression ratio : 2.5:1.
Fitting : 52mm dia. x 1.5mm pitch F/M thread.
Beam wander : 3 arc minutes max.beam expander diagram

The BEZ12 is based on a 3-element design using ZnSe lenses in black-anodised aluminium housings.
The input lens is mounted in a fixed position which is factory set to the ‘infinity’ focus (afocal)
position. Lenses (2) and (3) are moved axially in a complex motion driven by a precision-machined
cam, driven in turn by the zoom control ring (see figure 24.121).
Because the motion of lenses (2) and (3) is linear; that is, they do not rotate, beam-wander during
zoom operation is minimized.
The beam-wander of <3 arc minutes (about 1 milliradian) is specified for an incident beam aligned
to the optical axis of the BEZ12. With a misaligned input beam, the additional beam wander will be
71% of the misalignment error. See also data section 24.00.
Establishment of ideal processing parameters for cutting, welding and profiling at medium or low
Special test equipment.
Drilling variable hole diameters.
Associated equipment
Model BEZ12 attaches directly to ‘OPG’ optical piping (section 61.1). Lateral adjustment modules
LAU25 or LAM25 may be used to aid centration of the zoom beamexpander to the input beam
(sections 72.1, 72.2).