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4/26/2012
1
Introduction to LightTools TrainingIllumination in LightTools Ɣ Page 1
Copyright © 2012 Synopsys, Inc.
Illumination in LightTools
© Synopsys 2012 1 Introduction to LightTools, “Illumination in LightTools”
We’ll use LightTools to review fundamental concepts in illumination
© Synopsys 2012 2 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
LightTools Models the Interaction of Rays with Simulated Surfaces
ScatterRays can:
Refract
Reflect
Ab b
© Synopsys 2012 3 Introduction to LightTools, “Illumination in LightTools”
TIR
Absorb
Optical Properties Are Important!• Geometry alone does not determine light distribution• Optical Properties determine how the energy and direction
of a ray changesy g• Example: H7 Automotive lamp
© Synopsys 2012 4 Introduction to LightTools, “Illumination in LightTools”
All surfaces TIR With correct surface properties
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Copyright © 2012 Synopsys, Inc.
The Optical Properties in a Model Are Defined in the Optical Properties Manager
• Property zones choose from one of the optical properties in the OPM
• Use the OPM to:– Manage optical properties– Make changes to the model properties– Determine the list of current optical property assignments
© Synopsys 2012 5 Introduction to LightTools, “Illumination in LightTools”
Determine the list of current optical property assignments– Visualize the optical property assignments
The Optical Property Manager Interface Includes:
A list of existing Model and Default Properties
Controls for creating, loading
© Synopsys 2012 6 Introduction to LightTools, “Illumination in LightTools”
Controls for defining the optical property itself
and saving Model Properties
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Copyright © 2012 Synopsys, Inc.
OPM Navigation Tree Listing
• The OPM list is found in the system navigator
• Contains two sections– Model Properties: All of the optical
properties currently defined for the model– Default Properties: Optical property
definitions that are used when new surfaces are created (moved from the Preferences
© Synopsys 2012 7 Introduction to LightTools, “Illumination in LightTools”
are created (moved from the Preferences dialog box)
Assigning an Optical Property
• After an optical property is defined in the Model Properties list of the OPM, it will be available to be assigned to any property zoneproperty zone
• Assignment is made either through various context-sensitive menus or on the Property
Context menu
© Synopsys 2012 8 Introduction to LightTools, “Illumination in LightTools”
on the PropertyZone tab
List of available Model Properties
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Copyright © 2012 Synopsys, Inc.
Property Zone Tab
• The Property Zone tab displays several controls and summary information
Number of zones sharing this property
Drop-down for assigning optical properties
Open and Create controls similar to context menu
© Synopsys 2012 9 Introduction to LightTools, “Illumination in LightTools”
controls
Key summary information on current optical property
Editing Optical Properties
• Optical property definitions are freely changeable in the OPM
Modifications apply to all property• Modifications apply to all property zones currently assigned to that property
• The number of property zones that currently have the optical property assigned is shown in parentheses after the name of the property
© Synopsys 2012 10 Introduction to LightTools, “Illumination in LightTools”
the name of the property
• Properties in the Model Properties list can be deleted only when they are not assigned to any property zone– Use the context menu or the Delete key
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Copyright © 2012 Synopsys, Inc.
Usage Tab• A new Usage Tab provides summary tables for optical
property usage– Usage tabs are available for the whole model, each optical property,
and each entitand each entity
• The individual property usage tables show all the property zones to which the property is currently assigned– Shows the Solid, Primitive, Surface, and Zone names– Table can be sorted by column, as with any LightTools table
• The Model Properties usage tab displays all the zones in the model and their assigned optical properties
© Synopsys 2012 11 Introduction to LightTools, “Illumination in LightTools”
ode a d t e ass g ed opt ca p ope t es• Filter fields are provided at the top of the table
– Filters work on substrings - no wildcards needed
• User can select multiple rows and use the right-click context menu to change the assigned optical property for those zones
Usage TabSearch string filter fields
© Synopsys 2012 12 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
Custom Colors
• There are two modes for displaying surface colors in the 3D Design view
By Refract Mode: Displays the colors as a function of property– By Refract Mode: Displays the colors as a function of property type – identical to previous version of LightTools
– By Optical Property: Displays a user-defined color for each property zone
© Synopsys 2012 13 Introduction to LightTools, “Illumination in LightTools”
• To toggle between the two modes, use the menu View > Surface Color
Custom Color Example
By Refract Mode
By Optical Property
© Synopsys 2012 14 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
Work Along: Confirm Snells Law
• Snell’s law is:
• Air index of refraction (nair) is ~1.000
no*sin(ƍo)=n1*sin(ƍ1)no non1
ƍo ƍ1
ƍo
© Synopsys 2012 15 Introduction to LightTools, “Illumination in LightTools”
• Let’s make sure LightToolsagrees…
Start by Making a Block…• Enter the following:
– Block3Pt xyz 0,0,0 1 0.1
• Right click on it to open the optical properties. Check that it is Smooth optical and rays transmit
© Synopsys 2012 16 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
Non-Sequential (NS) Rays Can Be Used to Verify the Correct Interaction of Rays at Surfaces
� Each Non-Sequential ray starts with a relative power of 1.0
� The ray’s power drops at each f d t th t itt d
• Trace an NS ray through your block at an AOI 10o
– XYZ 0 0 -0 5 surface due to the transmittance and reflectance � Fresnel loss, scattering losses, and bulk
absorption are all taken into consideration
� Can trace individual rays, fans of rays, or grids of rays
XYZ 0,0, 0.5– Alpha: 10o
© Synopsys 2012 17 Introduction to LightTools, “Illumination in LightTools”
Why Did They Stop?• Each of the three rays shown below stops for a
different reasonTop Surface: Max Hits = 5
Surface set to absorb
Max Hits = 5
5
1
4
3
2
Surface set to split
© Synopsys 2012 18 Introduction to LightTools, “Illumination in LightTools”
Ray misses all other surfaces
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Copyright © 2012 Synopsys, Inc.
Ray Properties• Most properties are defined for the entire fan or grid of
rays, and are read-only for the individual segmentsRay stops when its power d b l 1%
Automatic: check if the surrounding region has amaterial
Description of
drops below 1%
© Synopsys 2012 19 Introduction to LightTools, “Illumination in LightTools”
pray fan
Wavelength for NSRays• Use Spectral Region Preferences to enter spectrum
Right-click in row to access menuaccess menu
LightTools can generate Blackbody
© Synopsys 2012 20 Introduction to LightTools, “Illumination in LightTools”
g yand Gaussian spectral distributions
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Copyright © 2012 Synopsys, Inc.
Accessing Ray Trace Data• Single ray trace data is very useful for troubleshooting
© Synopsys 2012 21 Introduction to LightTools, “Illumination in LightTools”
An NSRay traced through a light pipe (Fresnel Loss & Split)
Confirm the Behavior of an NS Ray through the Block• In the NS ray’s properties,
check the Incidence and Exit Angles of segment_1
• Does this make sense?– Check the Properties Tab of
this segment– Incidence: 10o
– Exit: 6.57o
g– nNBK7(550nm) = 1.5185– Snells law predicts 6.57o
Index following the interface
© Synopsys 2012 22 Introduction to LightTools, “Illumination in LightTools”
Incidence and Exit angles
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Copyright © 2012 Synopsys, Inc.
On a Real Optical Interface, Transmittance of Ray Will Drop Due to Fresnel Reflectance
• Currently, our ray transmits 100%– Fresnel reflectance is not
accounted for…yet! Current ray transmittance 100%
Fresnel Reflectance
Curves
© Synopsys 2012 23 Introduction to LightTools, “Illumination in LightTools”
Source: Wikipedia (http://en.wikipedia.org/wiki/Fresnel_equations)
Modify the Optical Property to Account for Fresnel Losses
• Open the Optical Properties Manager by double-click on it in the system navigator
• In the Model Properties> Transmitting>Smooth Optical window, change the Advanced Properties to Fresnel Loss– Press OK
Note that ALL 6 transmitting surfaces
© Synopsys 2012 24 Introduction to LightTools, “Illumination in LightTools”
– Note that ALL 6 transmitting surfaces will account for Fresnel losses
• Re-check the transmittance of the NS ray at segment_1
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Copyright © 2012 Synopsys, Inc.
Property Zones Let You Specify Different Optical Properties over a Surface
Refracting gproperty zone
© Synopsys 2012 25 Introduction to LightTools, “Illumination in LightTools”
Reflecting property zone
Work Along: Make a Lens…• Start a new model
(File>New)
• Enter the command:– Sketch4PtLens xyz 0,0,0
xyz 0,10,2 xyz 0,10,4 xyz 0,0,6 xyz 0,0,1
© Synopsys 2012 26 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
…add an NS ray fan…
• Add an NS ray fan– NSFanAIM xyz 0,-9,-5 xyz
0,9,-5 xyz 0,9,0y– Change it to a fan of 21 rays in
the Properties window
© Synopsys 2012 27 Introduction to LightTools, “Illumination in LightTools”
…and a dummy plane
• Add a dummy surface near the focal point so the NS rays are longer in the 3D window
• Dummy planes are defined by a vector that is normal to the plane
1st point
Plane
– DummyPlane xyz 0,0,30 xyz 0,0,20 • The length of the
vector is the half-diameter of the plane
2nd point
© Synopsys 2012 28 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
Surfaces Can Have None, One, or Multiple Property Zones Associated with Them• Each property zone can have a
different optical property
• All surfaces in LightTools have a BareSurface zone– An additional property zone is
automatically added to lens primitive surfaces
• Property zones supersede the B S f
© Synopsys 2012 29 Introduction to LightTools, “Illumination in LightTools”
BareSurface zone
• Additional property zones can be added to any surface by right clicking on the surface and choosing “Add Property Zone”
Add a Mirror Optical Property
• Right click on the LensFrontSurface and select Create and Assign gNew Optical Property– Make the new optical
property a Simple Mirror– Rename the optical
property to “Mirror”
© Synopsys 2012 30 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
Make the Center of the Lens Reflective by Changing the Optical Property of zone_1• Switch the optical
properties of LensFrontSurface>
BareSurface
BareSurface back to Transmitting_1
• LensFrontSurface>zone_1 should be the mirror– In the Geometry tab,
change the Radius to 5mm
zone_1
© Synopsys 2012 31 Introduction to LightTools, “Illumination in LightTools”
When Rays Split, Each Path Is Traced
• The power of each ray depends on reflectance and transmittance of the
90% transmittance 10% reflectance
and transmittance of the optical property 10 rays transmit.
With 90% power
© Synopsys 2012 32 Introduction to LightTools, “Illumination in LightTools”
10 rays reflect. With 10% power
10 rays start, which split into 20 rays (power is maintained)
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Copyright © 2012 Synopsys, Inc.
Probabalistic Ray Tracing Will Trace 1 Path
90% transmittance 10% reflectance
• Path of ray is determined probabilistically
9 out of 10 rays transmit. With 100% power
– Probability is determined by the transmittance and reflectance of the optical property
– Each path gets 100% power
© Synopsys 2012 33 Introduction to LightTools, “Illumination in LightTools”
1 out of 10 rays reflect. With 100% power
When You Need to Keep Track of Both Paths, Probabilistic Ray Tracing Is Efficient
All surfaces: Fresnel splitMax hits = 100Ray threshold = 1e-10
Receiver planeBacklight example
Probabilistic Ray Split: NO Probabilistic Ray Split: YES1 NS ray started in each model
y
Reflector and source
“Sawtooth” grating
© Synopsys 2012 34 Introduction to LightTools, “Illumination in LightTools”
2,000 rays started277,948 rays at receiverSimulation time: 50 minError estimate: 42%
2,000 [200,000] rays started 1,247 [118,969] rays at receiverSimulation time: 19 seconds [29 min]Error estimate: 44% [6%]
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Copyright © 2012 Synopsys, Inc.
The Distribution from a Real Light Source Is Simulated by Tracing Monte Carlo Rays
• These rays are accumulated on receivers, and are used to compute illumination analysis metrics– Illuminance: Spatial distribution of power– Intensity: Angular distribution of power– Luminance: Both angular and spatial components
© Synopsys 2012 35 Introduction to LightTools, “Illumination in LightTools”
Illuminance is Power/Area
• …or the spatial distribution of power• Photometric units: lux (lm/m2)• Radiometric units: W/m2
© Synopsys 2012 36 Introduction to LightTools, “Illumination in LightTools”
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Work Along: Illuminance in Space• Start a new model (File>New)
• Add a cylinder source at the origin:y g– XYZ 0,0,0– Radius: 1– Length: 0.1
© Synopsys 2012 37 Introduction to LightTools, “Illumination in LightTools”
Add Two Dummy Planes, and Add Receivers• Add two dummy planes
– One at Z=10, the other at Z=20– Width = Height = 10mm for both– DummyPlane xyz 0,0,10 xyz 0,0,15– DummyPlane xyz 0,0,20 xyz 0,0,25– Right click and “Add Surface
Receiver”
© Synopsys 2012 38 Introduction to LightTools, “Illumination in LightTools”
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Copyright © 2012 Synopsys, Inc.
We’ll Investigate Illuminance Differences Between the Two Dummy Planes• To define the cone, we’ll
specify the aim sphere of the sourcethe source
• Right click on the CylinderSource and go into Properties– In the emittance tab, change
M d O t Ai
© Synopsys 2012 39 Introduction to LightTools, “Illumination in LightTools”
Measured Over to Aim Region
– In the Aim Sphere tab, change the lower angle to 10o.
You Can Specify a Source to Emit Rays into a Specified Region to Trace Only the Rays You Care About
Aim areaAim sphere
Ray angles are confined to the aim cone
Rays trace into the aim area
© Synopsys 2012 40 Introduction to LightTools, “Illumination in LightTools”
Aim regions do not affect the relative power distribution from the source!
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Copyright © 2012 Synopsys, Inc.
Aim Sphere Controls• Upper angle
– Measured from +Z axis to –Z axis of aim sphere,
Z
U
Rays not emitted inthis region
mainly to clip the region defined by Lower Angle
• Lower Angle– Measured from +Z axis
to –Z axis of aim sphere
• Upper Angle < Lower Angle
Lowerangle
Upperangle
Rays emitted intothis annular zoneAim Sphere
Source
© Synopsys 2012 41 Introduction to LightTools, “Illumination in LightTools”
Angle• Collimated source:
– Upper angle = 0– Lower Angle = 0
Rays not emitted inthis region
Aim Sphere Limits…
To cover the whole sphere:upper = 0°, lower = 180°, alpha = any number, beta = any number
To cover the “upper” hemisphere:upper = 0°, lower = 90°, alpha = 90°, beta = 0°
To cover the “lower” hemisphere: upper = 0°, lower = 90°, l h 90° b t 0°
© Synopsys 2012 42 Introduction to LightTools, “Illumination in LightTools”
alpha = -90°, beta = 0°
To cover the “forward” 20°:upper = 0°, lower = 10°, alpha = 0°, beta = 0°
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Copyright © 2012 Synopsys, Inc.
Run a Simulation…
• Go to Ray Trace>Begin All Simulations
© Synopsys 2012 43 Introduction to LightTools, “Illumination in LightTools”
• To toggle the visibility of simulation rays in the 3D window:
Go to Ray Trace>Simulation Input, and press Begin Forward Simulation
Go to Ray Trace>Begin All Simulations
There Are Three Ways to Start a Simulation
Use the Begin Simulation icon in the 3D window
12
© Synopsys 2012 44 Introduction to LightTools, “Illumination in LightTools”
3
Modify simulation inputs…
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Analyzing the Illuminance
• Rename the receivers to:– “10mm Receiver”– “20mm Receiver”20mm Receiver
• Go to Analysis>IlluminanceDisplay>Lum Viewer– Pick the closer reciever
and press OK
10mm
20mm
© Synopsys 2012 45 Introduction to LightTools, “Illumination in LightTools”
and press OK
To switch receivers in the LumViewer…
View the Illuminance Pattern in the 3D Window• Right click on each
receiver and choose “Show Simulation Data”
• Visualizing illuminancedata in the 3D window is available for data on“Show Simulation Data” available for data on dummy plane receivers
© Synopsys 2012 46 Introduction to LightTools, “Illumination in LightTools”
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Illuminance Data and Statistics Can Be Viewed in the Illuminance Mesh Properties• Right click on each receiver to get to the illuminance
mesh’s properties
Error statistics (more later)
Total power ll d b
© Synopsys 2012 47 Introduction to LightTools, “Illumination in LightTools”
Raw mesh data
collected by the mesh
Mesh statistics
Intensity Is Power/Solid Angle• …or the angular distribution of power• Photometric units: Candela (lm/sr)• Radiometric units: W/sr• Radiometric units: W/sr
© Synopsys 2012 48 Introduction to LightTools, “Illumination in LightTools”
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The Intensity Over Collected by Our Two Receivers Is Identical!• Go to Analysis>Intensity
Display>LumViewer
Z=10mm Z=20mm
© Synopsys 2012 49 Introduction to LightTools, “Illumination in LightTools”
Intensity meshes only use the angular information from each
ray…in this case, both receivers collect the same data
Luminance Is Power/Area/Solid Angle• Collect power as a function of spatial
position and angular direction– “Brightness” is our perception of luminance
• Photometric units: Nits (lm/m2/sr)
• Radiometric units: W/m2/sr
© Synopsys 2012 50 Introduction to LightTools, “Illumination in LightTools”
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Spatial vs. Angular Luminance
• Spatial Luminance Meter– Collect rays over a spatial
region, and limit the angle
• Angular Luminance Meter– Collect rays over an entire
hemisphere, and limit the – Like a spot meter area
Luminance collected using
fixed area
Luminance collected
© Synopsys 2012 51 Introduction to LightTools, “Illumination in LightTools”
Plotted as a function of angle
Luminance collected using a fixed or scanning angle
Plotted as a function of spatial position
Model a Thin Diffuser Using a Thin Block with a Lambertian Scatterer• Open the Optical Properties
Manager. Add a Simple Scatterer> Lambertian– In the Lambertian tab, change
the ray trace mode to transmit– A lambertian scatterer scatters
light with uniform luminance over the entire hemisphere
• Make a thin block just in front of the first receiver
© Synopsys 2012 52 Introduction to LightTools, “Illumination in LightTools”
– Block3pt xyz 0,0,9.8 10 0.1– Make the material air
• Change the optical property of the Block’s RightSurface to Lambertian
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Copyright © 2012 Synopsys, Inc.
Run a Simulation and Compare the Intensity and the Angular Illuminance• In the Receiver
Properties>Forward Simulation enable a spatialSimulation, enable a spatial and angular luminance chart for each receiver
• Run a simulation with 100,000 rays
• Go to Analysis>Intensity>LumViewer
© Synopsys 2012 53 Introduction to LightTools, “Illumination in LightTools”
• Go to Analysis>Angular Luminance>LumViewer
Intensity vs. Illuminance vs. Luminance of a Lambertian Scatterer10mm Receiver The adjacent receiver collects nearly all angles
Intensity Angular Luminance Illuminance Spatial
Luminance
© Synopsys 2012 54 Introduction to LightTools, “Illumination in LightTools”
20mm Receiver The spacing between the receivers limits the cone of collected rays
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Copyright © 2012 Synopsys, Inc.
How Are Rays Collected on a Receiver Mesh?• Receiver data is usually divided into rectangular grids to
analyze ray data• Data can be displayed as numbers/color maps
Rays on receiver Îprobably not very useful form for analysis
Receiver surface is divided into a rectangular grid (# rays/cell is shown)
© Synopsys 2012 55 Introduction to LightTools, “Illumination in LightTools”
(Ray power)/ (# Samples) for each cell
(Ray power)/ (# Samples) as a false color map
Importance of Mesh Size• Mesh dimensions (size) control the “resolution” and
“accuracy” of the results2 mm 2 mm
2 m
m
© Synopsys 2012 56 Introduction to LightTools, “Illumination in LightTools”
5x5 Mesh Î larger cells Îlower spatial resolution (0.4 mm)2 and more rays per cell Îhigher accuracy
8x8 Mesh Î Smaller cells Î Higher spatial resolution (0.25 mm)2 and fewer rays per cell Î lower accuracy
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Copyright © 2012 Synopsys, Inc.
Receiver Mesh Types• Each receiver type can have several
types of “meshes”– Different meshes for different types of
data
• Surface receiver– Illuminance mesh (Irradiance,
Illuminance)– Intensity mesh (Intensity)– Spatial luminance mesh (Luminance)
Angular luminance mesh (Luminance)
© Synopsys 2012 57 Introduction to LightTools, “Illumination in LightTools”
– Angular luminance mesh (Luminance)– CIE meshes (Chromaticity and CCT)
• Far field receiver– Intensity mesh (Intensity)– CIE meshes (Chromaticity and CCT)
The Accuracy Is Determined by the Number of Rays Falling in Each Bin (Ray Density)• Every cell in the mesh has a certain error due to statistical
noise. The peak error estimate is the first standard deviation of the receiver cell with the maximum illuminance or intensityof the receiver cell with the maximum illuminance or intensity value and is given by the following formula:
( )¦¦
N
N
f
f=
2
!N
= 1!
Converges when f is constant
© Synopsys 2012 58 Introduction to LightTools, “Illumination in LightTools”
where f = irradiance or intensity of each ray
N = total number of rays traced from one source
This is the Error Estimate for each bin
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54% of 5,000 rays11 x 11 gridPeak error 16.8%
54% of 5,000 rays5x 5 gridPeak error 8.9%
54% of 240,000 rays11x 11 gridPeak error 2.9%
Binning Effects
© Synopsys 2012 59 Introduction to LightTools, “Illumination in LightTools”
• Note the tradeoff between spatial resolution (grid size) and peak error
• Larger numbers of rays must be traced to get enough rays per bin for better accuracy
Rays That Are Below the Relative Ray Power Threshold Will Be Terminated• As a ray interacts with your
model, there will typically be l t h flosses at each surface interaction and through many volumes
• The Relative Ray Power Threshold controls the threshold that the power of a
d t b f it iWhen you have significant scattering in your model
© Synopsys 2012 60 Introduction to LightTools, “Illumination in LightTools”
ray can drop to before it is terminated
• For a simulation, this control is available in the Ray Trace>Simulation Inputs…– The default is 1%
scattering in your model, consider this threshold
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Working with LightTools Geometry
• Coordinate systems
• Entities/primitives
• Euler angles
© Synopsys 2012 61 Introduction to LightTools, “Illumination in LightTools”
• Ray Trace Acceleration
Coordinate Systems� LightTools has a global coordinate system and a
local coordinate system (also known as UCS, or user coordinate system)y )� By default they are coincident� Both coordinate systems are right-handed
Global Coordinate System
© Synopsys 2012 62 Introduction to LightTools, “Illumination in LightTools”
Local Coordinate System (or UCS)
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Surface Coordinate System� Each surface has a local coordinate system identified
with it� The z-axis of each surface coordinate system points
d f h lidoutward from the solid� Place UCS on surface to see coordinate system
orientation
Place UCS on surfaceReturn UCS to global
© Synopsys 2012 63 Introduction to LightTools, “Illumination in LightTools”
Global coordinatesystem(black axes)
Local coordinate system(colored axes)
User Coordinate System - UCS � The UCS can be shifted and rotated with respect to
the global coordinate system with UCS Preferences � View > View UCS > UCS Preferences or� UCS tab of the 3D view preferences
© Synopsys 2012 64 Introduction to LightTools, “Illumination in LightTools”
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Defining New UCS� The UCS axes can also be
aligned with the coordinate system of a surface or ray using the command palette
� Sketched objects are entered aligned with or oriented relative to the UCS Z-axis.� Useful for entering tilted
subsystems
Move origin
Rotate aboutorigin
Place on reference
© Synopsys 2012 65 Introduction to LightTools, “Illumination in LightTools”
Place on surface
Mouse clicks:define origin & 2coordinate axes
Place on line
coordinate system
Point Entry Is Very Flexible� LightTools keeps track of the location of the
current point (location of the last point entered)
� A new point can be entered in absolute terms or as a change (delta) from the current point
� Points can be entered in global, UCS, or pane coordinates
© Synopsys 2012 66 Introduction to LightTools, “Illumination in LightTools”
coordinates
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How to Enter Points on the Command Line� The basic command for entering a point globally is
XYZ x,y,z
� The x, y, z coordinates are separated by commas (no white space)space)
� White space is used before and after the coordinates� Points can also be given in UCS (local) coordinates
LXYZ x,y,z
� Points can also be given in pane coordinatesUVW u,v,w
� U is horizontal in the pane V is vertical in the pane W is
© Synopsys 2012 67 Introduction to LightTools, “Illumination in LightTools”
� U is horizontal in the pane, V is vertical in the pane, W is perpendicular to the pane
� All forms are converted internally to XYZ form
Entering Points Relative to Current Point
� A point can also be expressed as a change (delta) l ti t th t i t i l b l l lrelative to the current point in global, local, or pane
coordinates� The delta can be a linear delta or a length and an angle
� Linear delta formsDXYZ dx,dy,dz delta in global coordinatesLDXYZ dx,dy,dz delta in local coordinatesDUV d d d d lt i di t
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DUV du,dv,dw delta in pane coordinate
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Entering Points as Angular Deltas� Points can also be entered as length and angle from
current point� Most useful form:
LA l," delta length and angle (in pane)
o
90o
"
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0o
la 2,0 la 1,45 la 2,0 la 1,90 la 1,0
Point Entry ExamplesXYZ 0,0,0 global origin
UVW 0,0,0 origin in pane (keep depth)
DXYZ 1,2,3 shift 1 in x, 2 in y, 3 in z (global)
DUV 1,2,0 shift 1 right, 2 up in pane (keep depth)
LA 2,45 shift length 2, 45° in pane
; repeat last entered point (global)
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Euler Angle Rotations• Rotations described by the optical Euler angles:
– Order is important! For multiple angles, Alpha rotation 1st, then Beta about the newly defined axes, then Gamma about the axes resulting from the Alpha and Beta rotationsresulting from the Alpha and Beta rotations
– Convention:í Alpha: positive for “+Z to +Y”í Beta: positive for “+X to +Z”í Gamma: positive for “+X to +Y”
+x
+y
+z
+z'+y'
# +x
+y
+z+x'
+y
+z
+y'+x' $
+x
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+x # +x+z'
%+x
Alpha > 0 Beta > 0 Gamma > 0
Example: Coordinate Rotation
# = 45 % = $ = 0
X-Y plane Y-Z plane
% = $ = 0
# = 45 % = 30$ = 0
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# = 45 % = 30$ = 10
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Entity and Primitive Coordinates• Example: Cylinder subtracted
from block– Entity reference point = reference
point of the blockpoint of the block – 2 primitives:
í Block located at XYZ = 0, 0.5, 0.5; Alpha = 20
í Cylinder located at XYZ = 0, 1.7789, 4.0755; Alpha = - 7.123)
Subtract
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Resulting “entity”
Entity referencepoint
Coordinates - Entity• Entity coordinates are equal to the global coordinates of
the block before the Boolean
• The entity (cube primitive + cylinder primitive) will move• The entity (cube primitive + cylinder primitive) will move together when the entity is moved
• Properties associated with the entity: – Material– Ray Traceable– Immersion
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Immersion
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Coordinates – Cube Primitive• The “Absolute” coordinates of the cube primitive is
unchanged
• The “Relative” coordinates remain zero since the entity• The Relative coordinates remain zero since the entity reference point is the same as the cube primitive’s reference point
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Coordinates – Cylinder Primitive• The “Absolute” coordinates of the cylinder primitive are
unchanged
Th “R l ti ” di t h h d i th• The “Relative” coordinates have changed since the reference point of the “entity” is now different
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Move Cylinder Primitive• The relative coordinates of the cylinder changed
– The new position of the cylinder is 3 units in +Z direction (global) from the entity referenceTh i t ti i 20 d ith t t th– The new orientation is 20 degrees with respect to the entity
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Rotate Entity• If the entity is rotated, the
cylinder primitive will keep the same “relative” angle to the entityto t e e t ty
• The absolute position/angle of the cylinder primitive will change
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Move Cube Primitive
• If the relative position of the cube is changed, the entity will still keep its referencewill still keep its reference point
Entity moved to XYZ=0,0,0 and
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the cube primitive moved to (relative) XYZ=0,-1,1
Relative Coordinates Are Important
• Relative coordinates give an excellent way to handle primitives with respect to the Boolean entityentity– No need to have any knowledge about a given
primitive’s global coordinates– Position and orientation can be specified relative to
the entity reference
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Precision Ray Trace vs. Ray Trace Acceleration• Simulations will run faster if
the geometry is set to run in Ray Trace Acceleration– The geometry is approximated
as a set of facets– Up to 100x speed improvement
• The ray trace speed will improve, but the ray trace accuracy will degrade!– The level of degradation
depends on the model
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depends on the model– At the early stages of design,
the degradation may be acceptable
– For the final stages of design, use High Accuracy or Precision mode for simulations
Ray Trace Mode Is Set at the Global or Object Level
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There’s a lot more to illumination and LightTools, but this will get you started!
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