FOCUS LENS ASSEMBLIES
Series LFL Single and Multiple Element
As an integral part of each of the Series LBD Laser Beam Delivery Systems, Lee Laser
includes one or more focus lens assemblies. These are the final optical element in the
system, and focus the beam onto the users workpiece.
All focus lens assemblies (sometimes also called objective lenses) contain lenses of high
quality, fused silica glass. Lens surfaces are antireflection (AR) coated for the 1064-nm
fundamental wavelength of our Nd:YAG lasers. Special AR coatings are available for use
with laser models which operate at 532 and 1320 nm.
Each lens assembly includes a precision machined, black hardcoated, aluminum housing with
mounting threads at the output end. This permits easy removal and replacement should the
operator wish to use another lens assembly with a different focal length.
Single Element Lens Assemblies
Common focus lenses are typically of two types:
a. Plano-convex
b. Bi-convex
one surface is flat, the other is spherical
both surfaces are spherical with the same curvature
In both cases. these lenses exhibit significant spherical aberration which limits fine focus
capability.
Lee Laser uses best-form lenses which are computer designed to correct for spherical
aberration. The two surfaces of best-form lens have different radii of curvature. As a result,
best-form lenses produce superior focus beam quality especially where the fine focus of
TEMoo-mode beam is required.
The table below lists our most common models:
Model
Focal Length
Work Distance
LFL-S75
LFL-S100
LFL-S150
75 mm
100 mm
150 mm
65 mm
90 mm
140 mm
2
Multiple Element Lens Assemblies
Lee Laser's multiple-element lens assemblies are used when a shorter focal-length to beamdiameter ratio (F#) is necessary. As with best-form lenses, multi-element lens assemblies are
computer corrected for spherical aberrations. Whereas best-form lenses are generally limited
to minimum F# 8 for critical TEMoo applications, a multi-element lens assembly may be used
for focal situations where the F# may be as small as 2.5.
Multi-element assemblies are designed to accommodate the high average power and high
peak pulse power of Lee Laser's most powerful lasers. For this reason, the lenses are airspaced with no optical cement between them.
Lee Laser offer three multi-element lens assemblies:
Model
Focal Length
Work Distance
LFL-M37
LFL-M55
LFL-M60
LFL-M77
LFL-M90
37 mm
57 mm
60 mm
77 mm
90 mm
26 mm
55 mm
50 mm
70 mm
78 mm
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Super Apochromat
Super Apochromat