Zeyu Zhao
OPTI 521
12/18/2015
Tolerancing is an important skill to have as
an optical engineer.
Having designed a lens, it is important to
know how it will perform once it is built.
Define quantitative figures of merit for the
requirements
Estimate system tolerances
◦ Component manufacturing tolerances
◦ Mechanical alignment tolerances
◦ Optical tolerances
Execute Zemax tolerance analysis
Review tolerance results
Adjust tolerances appropriately. Keep cost
and schedule in mind
Define quantitative figures of merit for the
requirements
Estimate system tolerances
◦ Component manufacturing tolerances
◦ Mechanical alignment tolerances
◦ Optical tolerances
Execute Zemax tolerance analysis
Review tolerance results
Adjust tolerances appropriately. Keep cost
and schedule in mind
Must propagate all performance specs
through to assembly
Typical requirements
◦ RMSWE (Root Mean Square Wavefront Error)
◦ MTF at particular spatial frequencies
◦ Distortion
◦ Fractional encircled energy
◦ Beam divergence
◦ Geometric RMS image size
◦ Dimensional limits
Define quantitative figures of merit for the
requirements
Estimate system tolerances
◦ Optical tolerances
◦ Component manufacturing tolerances
◦ Mechanical alignment tolerances
Execute Zemax tolerance analysis
Review tolerance results
Adjust tolerances appropriately. Keep cost
and schedule in mind
Parameter Base Precision High precision
Lens diameter 100 µm 25 µm 6 µm
Lens thickness 200 µm 50 µm 10 µm
Radius of curvature 20 µm 1.3 µm 0.5 µm
Surface sag 1% 0.1% 0.02%
Value of R
Wedge (light deviation) 6 arc min 1 arc min 15 arc sec
Surface irregularity 1 wave λ/4 λ/20
Surface finish 50 Å rms 20 Å rms 5 Å rms
Scratch/dig 80/50 60/40 20/10
Dimension tolerances for complex 200 µm 50 µm 10 µm
elements
Angular tolerances for complex 6 arc min 1 arc min 15 arc sec
elements
Bevels (0.2 to 0.5 mm typical) 0.2 mm 0.1 mm 0.02 mm
± 1 mm for coarse dimensions that are not
important
± 0.25 mm for typical machining without
difficulty
± 0.025 mm precision machining, readily
accessible
< ± 0.002 mm high-precision, requires
special tooling
Parameter Base Precision High precision
Spacing (manual machined
200 µm 25 µm 6 µm
bores or spacers)
Spacing (NC machined bores
50 µm 12 µm 2.5 µm
or spacers)
Concentricity (if part must be
removed from chuck 200 µm 100 µm 25 µm
between cuts)
Concentricity (cuts made
200 µm 25 µm 5 µm
without de-chucking part)
Define quantitative figures of merit for the
requirements
Estimate system tolerances
◦ Component manufacturing tolerances
◦ Mechanical alignment tolerances
◦ Optical tolerances
Execute Zemax tolerance analysis
Review tolerance results
Adjust tolerances appropriately. Keep cost
and schedule in mind
Zemax conducts an analysis of the tolerances
using one of these three tools:
◦ Sensitivity analysis
◦ Inverse sensitivity analysis
◦ Monte Carlo analysis
“Forward” analysis
Considers each defined tolerance sequentially
and independently.
Parameters are adjusted to the limits of the
tolerance range, and then the optimum value
of each compensator is determined.
A table is generated listing the contribution
of each tolerance to the performance loss.
“Backwards” analysis
Iteratively computes the tolerance limits on
each parameter when the maximum
degradation in performance is defined.
All tolerances are considered at once.
Random systems are generated using the
defined tolerances.
Every parameter is randomly perturbed using
appropriate statistical models. All
compensators are adjusted and then the
entire system is evaluated with all defects
considered.
Let’s open Zemax file DOUBLET.ZMX
Presenting in Zemax
