BEZ25 Zoom BeamexpanderBEZ25 zoom beam expander


Model BEZ25 zoom beamexpander is a high specification unit with a low beam compression ratio, designed
for use with CO2 lasers having up to 20mm beam diameter and 2000W CW power.
Notable features of model BEZ25 include:
* Excellent beam pointing accuracy.
* Output beam focus control.
* Water cooling.
The focus control, combined with variable magnification, allows the user of model BEZ25 to achieve ideal
downstream laser beam conditions from a variety of input beam parameters.
Technical specifications
Dimensions : see figure 24.261.
Weight : 2.4 kg.
Cooling : water cooled.
Focus range : +8m, through ‘infinity’ to -8m.
Zoom range : x1.2 to x1.9, continuously variable.
Output clear aperture : 35mm diameter.
Input clear aperture : 25mm, (18.4mm usable at M = x1.9).
Beam compression ratio : 1.4:1.
Fitting (2 ends) : 52mm dia. x 1.5mm pitch F/M thread.
Beam wander : <30 arc seconds.

The BEZ25 has a 3-element design using ZnSe lenses in black-anodised aluminium housings.
The two input lenses provide the zoom magnification and are contolled by means of an external zoom control
ring. Lens (3) is moved axially to provide beam focus control and this motion is effected by means of an external
focus ring.
All lenses are centred within their mounting cell to accuracies of a few arcseconds and each cell contains linear
bearings running on precision-ground steel rods which run the whole length of the unit.
During zoom or focusing action, there is no rotation of any lens, and so the assembly has a very high level of
inherent centration accuracy, minimizing beam wander.
The beam wander of <30 arcseconds (about 0.1 milliradian) is specified for an incident beam aligned to the optical
axis of the BEZ25. With a misaligned input beam, the additional beam wander will be 31% of the misalignment
error when taken over the full zoom magnification range. See also data section 24.00.
Allows some commonality of beam properties to be obtained from a variety of different laser sources.
Establishment of ideal processing parameters for cutting, welding and profiling at medium laser powers.
Special test equipment.
Drilling variable hole diameters.
Associated equipment
Model BEZ25 attatches 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).
In order to obtain the best beam-pointing performance from the BEZ25 beamexpander, the input beam alignment
is critical. A fine-tilt adjustment unit, TAU25, is available as an accessory.
(See section 72.8).