“WFF” Series – Wide-Field Focussing
WFF series lenses are 3-element assemblies designed to operate with an angular field-of-view of ±6
degrees. Laser beams entering the input of the lens at an angle are focused to a diffraction-limited
spot off-centre in a flat image plane. Applications requiring lenses which have this function are
unusual in laser optics, but do exist in certain scanning systems and in multi-beam systems producing
an array of spots in the focal plane. Where the optimum power density is required in an axicon
system, (ring-focus – see Section 7.0), then a ‘WFF’ series lens would give the best performance. The
lenses are designed for use at 10.6μm. The forward vee groove allows mounting of a gas manifold.
Clear aperture : 27.0mm all models.
Lens material : Lasergrade ZnSe.
Coatings : All surfaces have low absorption anti-reflection coatings.
Sealing : Sealed against dust. Not intended for high gas pressure use.
Cell material : Aluminium HE30.
Finish : Black anodised.
Cell size : See Figure 26.31.
The associated equipment is specialized and not otherwise detailed in ULO Optics literature. It
includes a variable-separation twin-spot unit and a multi-spot unit for simulation of electrostatic perforation
in cigarette filter tipping applications.