optical design with zemaxdesign... · 1. photometry 2. illumination calculation 3. light sources 4....
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Optical Design with Zemax
Lecture 9: Illumination
2013-06-14
Herbert Gross
Summer term 2013
2
Preliminary Schedule
1 12.04. Introduction
Introduction, Zemax interface, menues, file handling, preferences, Editors, updates,
windows, coordinates, System description, Component reversal, system insertion,
scaling, 3D geometry, aperture, field, wavelength
2 19.04. Properties of optical systems I Diameters, stop and pupil, vignetting, Layouts, Materials, Glass catalogs, Raytrace,
Ray fans and sampling, Footprints
3 26.04. Properties of optical systems II
Types of surfaces, Aspheres, Gratings and diffractive surfaces, Gradient media,
Cardinal elements, Lens properties, Imaging, magnification, paraxial approximation
and modelling
4 03.05. Aberrations I Representation of geometrical aberrations, Spot diagram, Transverse aberration
diagrams, Aberration expansions, Primary aberrations,
5 17.05. Aberrations II Wave aberrations, Zernike polynomials, Point spread function, Optical transfer
function
6 24.05. Optimization I
Principles of nonlinear optimization, Optimization in optical design, Global
optimization methods, Solves and pickups, variables, Sensitivity of variables in
optical systems
7 31.05. Optimization II Systematic methods and optimization process, Starting points, Optimization in Zemax
8 07.06. Imaging Fundamentals of Fourier optics, Physical optical image formation, Imaging in Zemax
9 14.06. Illumination Introduction in illumination, Simple photometry of optical systems, Non-sequential
raytrace, Illumination in Zemax
10 21.06. Advanced handling I
Telecentricity, infinity object distance and afocal image, Local/global coordinates, Add
fold mirror, Scale system, Make double pass, Vignetting, Diameter types, Ray aiming,
Material index fit
11 28.06. Advanced handling II Report graphics, Universal plot, Slider, Visual optimization, IO of data,
Multiconfiguration, Fiber coupling, Macro language, Lens catalogs
12 05.07. Correction I
Symmetry principle, Lens bending, Correcting spherical aberration, Coma, stop
position, Astigmatism, Field flattening, Chromatical correction, Retrofocus and
telephoto setup, Design method
13 12.07. Correction II Field lenses, Stop position influence, Aspheres and higher orders, Principles of glass
selection, Sensitivity of a system correction, Microscopic objective lens, Zoom system
14 12.07. Physical optical modelling Gaussian beams, POP propagation, polarization raytrace, polarization transmission,
polarization aberrations
1. Photometry
2. Illumination calculation
3. Light sources
4. Illumination systems
5. Special illumination components
6. Illumination in Zemax
3
Contents
dW
s
dAS
qS
n
Differential Flux
Differential flux of power from a
small area element dAs with
normal direction n in a small
solid angle dΩ along the direction
s of detection
Integration of the radiance over
the area and the solid angle
gives a power
S
SS
S
AdsdL
dAdL
dAdLd
W
W
W
qcos
2
PdA
A
4
Transfer of Energy in Optical Systems
General setup
Optical SystemRadiation
Source
Detector
dA DdAS
in out
PS PD
Ref: B. Dörband
Optical System
A2
d2
dA1dW2W2
2
2
2
f
P1
q1
qR
1
W1
Detector
r
dA
5
Illumination Fall-off
Irradiance decreases in the image field
Two reasons:
1. projection due to oblique ray bundles
2. enlarged distances along oblique chief rays
Natural vignetting: smooth function
depends on: 1. stop location
2. distortion correction
entrance
pupil
y yp
chief ray
chief ray
exit
pupil
y' y'p
w'
w
R'Ex
U
axis bundle
off axis
bundle
marginal
ray
E(y) E(y')U'
6
Natural Vignetting
Consideration with the help of entrance and exit pupil:
1. transfer from source to entrance pupil
2. transfer between pupils
3. transfer from exit pupil into image plane
'cos
cos
'' 4
422
w
w
s
s
dA
dA
n
n
dA
dA
AP
EP
EP
AP
object entrance
pupil
exit
pupilimage
sp
dA
dAEN
dAEX
dA'
U w
q
U'
w' q'
system
marginal
ray
chief ray
s'p
7
Natural Vignetting: System with Front Stop
Exact integration:
similar to general formula
including differential magnification
Special case on optical axis
Approximation small aperture
Special case circular symmetry
Appropriate distortion allows to correct the natural vignetting effect
2/1
222
22
tancos1
tancos411
'2)('
uw
uw
dA
dALwE
wEwE 4cos)0(')('
udA
dALE 2sin
')0('
'
''
dh
dh
h
h
dA
dAmA
E L u kh
h
dh
dhw fcorr' sin
'
'cos 2 4
8
Special problems in the layout of illumination systems:
1. complex components: segmented, multi-path
2. special criteria for optimization:
- homogeneity
- efficiency
3. incoherent illumination: non-unique solution
Illumination Systems
Non-Sequential Raytrace: Examples
3. Illumination systems, here:
- cylindrical pump-tube of a solid state laser
- two flash lamps (A, B) with cooling flow tubes (C, D)
- laser rod (E) with flow tube (F, G)
- double-elliptical mirror
for refocussing (H)
Different ray paths
possible
A: flash lamp gas
H
4
B: glass tube of
lamp
C: water cooling
D: glass tube of cooling
5
6
3
2
1
7
E: laser rod
F: water cooling
G: glass tube of cooling
10
Simple raytrace:
S/N depends on the number of rays N
Improved SNR: raytube propagation transport of energy density
Illumination Simulation
N = 2.000 N = 20.000 N = 200.000 N = 2.000.000
N = 100.000
0
1
-0.5 -0.3 -0.1 0.1 0.3 0.50
1
-0.5 -0.3 -0.1 0.1 0.3 0.50
1
-0.5 -0.3 -0.1 0.1 0.3 0.5
N = 10.000 N = 63
NTR
= 63 NTR
= 63 NTR
= 63
CAD model of light sources:
1. Real geometry and materials
2. Real radiance distributions
Bulb lamp
XBO-
lamp
Realistic Light Source Models
-2
0
2-8
-6
-4
-2
0
2
4
6
8
0
0.5
1
z
intensity I
[a.u.]
x
Gaussian Beam Propagation
Paraxial transform of
a beam
Intensity I(x,z)
2
)(2
2 )(
2),(
zw
r
ezw
PzrI
Angle Indicatrix Hg-Lamp high Pressure
cathode
0
800
1200
1600
0 1020
30
40
50
60
70
80
90
100
110
120
130
140
150
160170
180190200
210
220
230
240
250
260
270
280
290
300
310
320
330
340350
400
azimuth angles :
30°50°
70°
90°
110°
130°
150°
Polar diagram of angle-dependent
intensity
Vertical line:
Axis Anode - Cathode
XBO-
lamp
Xenon lamp Line spectrum
HG-Xe-lamp
Spectral Distributions
I
1
0.5
0380 580 780 980
I
1
0.5
0380 580 780 980
source
collector condenser objective
lens
object
plane
image
plane
field stop aperture stopback focal plane -
pupil
Köhler Illumination Principle
Principle of Köhler
illumination:
Alternating beam paths
of field and pupil
No source structure in
image
Light source conjugated
to system pupil
Differences between
ideal and real ray paths
condenser
object
plane
aperture
stopfield
stop filter
collector
source
Illumination Optics: Collector
Requirements and aspects:
1. Large collecting solid angle
2. Correction not critical
3. Thermal loading
large
4. Mostly shell-structure
for high NA
W(yp)
200
a) axis b) field
200
W(yp)
yp
480 nm
546 nm
644 nm
yp
W(yp)
200
a) axis b) field
200
W(yp)
yp
yp
480 nm
546 nm
644 nm
Illumination Optics: Condenser
2. Abbe type, achromatic, NA = 0.9 , aplanatic, residual spherical
3. Aplanatic achromatic, NA = 0.85
y'100m
a) axis b) field
yp
480 nm
546 nm
644 nm
y'100m
yp
x'100m
xp
tangential sagittal
y'100m
a) axis b) field
yp
480 nm
546 nm
644 nm
y'100m
yp
x'100m
xp
tangential sagittal
Fresnel Surfaces
Special description of Fresnel surfaces
with circular symmetry
Bezier spline desciption with corresponding
choice of the control points:
modelling of edges
Mathematically:
- surface sag continuous
- derivative with steps
19
Lighthouse optics
Fresnel lenses with height 3 m
Separated segments
Complex Geometries
Illumination Components
Solar concentrator optics
Ref: Light Presciptions Innovations
Arrays - Illumination Systems
Illumination LED lighting
Ref: R. Völkel / FBH Berlin
Principle of a light pipe / slab integrator:
Mixing of flipped profiles by overlapping of sub-apertures
Spatial multiplexing, angles are preserved
Number of internal reflexions determine the quality of homogeneity
Rectangular Integrator Slab
length L
width
asquare
rod
virtual
intersection
point
point of
incidence
exit
surface
Ideal homogenization:
incoherent light without interference
Parameter:
Length L, diameter d, numerical aperture angle q, reflectivity R
Partial or full coherence:
speckle and fine structure disturbs uniformity
Simulation with pint ssource and lambert indicatrix or supergaussian profile
Rectangular Slab Integrator
x
I(q)
x'
I(x')q
d
L
Rectangular Slab Integrator
Full slab integrator:
- total internal reflection, small loss
- small limiting aperture
- problems high quality of end faces
- also usable in the UV
Hollow mirror slab:
- cheaper
- loss of 1-2% per reflection
- large angles possible
- no problems with high energy densities
- not useful in the UV
slab integrator
hollow integrator
Array of lenslets divides the pupil in supabertures
Every subaperture is imaged into the field plane
Overlay of all contributions gives uniformity
Problems with coherence: speckle
Different geometries: square, hexagonal, triangles
Simple setup with one array
Improved solution with double array and additional
imaging of the pupil
Flyeye Array Homogenizer
farrD
arr
xcent
u
xray
Dsub
subaperture
No. j
change of
direction
condenser
1 2 3 5
array
4
focal plane of the
array
receiver
plane
starting
plane
farr
fcon
Dill
Dsub
Flyeye Array Homogenizer
condenserarray
spherical surface with
secondary source
points
illumination
field
Simple model: Secondary source of a pattern of point sources
Types of surfaces:
Mirror with facets
Regular lenslet array
Statistical lenslets
Segmented Surfaces and Arrays
bearbeitete
Fläche
einfallender
Strahl
Facetten-
spiegel
Flyeye Array Homogenizer
a b
Example illumination fields of a homogenized gaussian profile
a) single array
b) double array
- sharper imaging of field edges
- no remaining diffraction structures
Generation of a ring profile
Axicon:
cone surface with peak on axis
Ringradisu in the focal plane
of the lens
Ring width due to diffraction
fnR )1(
a
fR
22.1
Axicon Lens Combination
R
o
ff
a
R
o
f
Illumination Optics: Condenser
2. Epi-illumination
Complicated ring-shaped components
around objective lens
object
ring lens
illuminationobservation
object
ring lens
illuminationobservationcircle 1
circle 2
Simple options:
Relative illumination / vignetting for systems with rotational symmetry
Advanced possibility:
- non-sequential component
- embedded into sequential optical systems
- examples: lightguide, arrays together with focussing optics, beam guiding,...
General illumination calculation:
- non-sequential raytrace with complete different philosophy of handling
- object oriented handling: definition of source, components and detectors
32
Illumination in Zemax
Relative illumination or vignetting plot
Transmission as a function of the field size
Natural and arteficial vignetting are seen
33
Relative Illumination
0 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25
y field in °
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
relative
illumination
natural vignetting
cos4 w
onset of
truncation
total
illumination
vignetting
Partly non-sequential raytrace:
Choice of surface type ‚non-sequential‘
Non-sequential component editor with many control parameters is used to describe the
element:
- type of component
- reference position
- material
- geometrical parameters
Some parameters are used from the lens data editor too:
entrance/exit ports as interface planes to the sequential system parts
34
Illumination in Zemax
Example:
Lens focusses into a rectangular lightpipe
35
Illumination in Zemax
Complete non-sequential raytrace
Switch into a different control mode in File-menue
Defining the system in the non-sequential editor, separated into
1. sources
2. light guiding components
3. detectors
Various help function are available to
constitue the system
It is a object (component) oriented philosophy
Due to the variety of permutations, the raytrace
is slow !
36
Illumination in Zemax
Many types of components and options are available
For every component, several
parameters can be fixed:
- drawing options
- coating, scatter surface
- diffraction
- ray splitting
- ...
37
Illumination in Zemax
Starting a run requires several control
parameters
Rays can be accumulated
38
Illumination in Zemax
Typical output of a run:
39
Illumination in Zemax
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