FRED Overview FRED: A software tool for modern engineering

What is FRED? FRED Introduction Comprehensive opto-mechanical systems design analysis tool Stray light analysis (scatter and ghosting) Coherent beam propagation Imaging system design and photo-realistic rendering Virtual prototyping Opto-mechanical systems debugging (Forensic Optics) Thermal self-emission analysis Illumination design Tolerancing, fabrication and testing Both sequential and non-sequential raytracing modes Multi-variable optimization capability

What is FRED? FRED Introduction FRED FRED can be used in virtually every step of the design process. Initial proof of concept using catalog parts Integration of optical and CAD designs Full analysis of a virtual prototype including scatter, coatings, dispersion, absorption, volume scatter, diffraction, thermal emission, source characteristics… Quickly manipulate model parameters for tolerance analyses Integration with vendor catalogs for manufacturing or system debugging Concept 1 FRED Design 2 Analysis 3 4 Tolerancing 5 Manufacture

FRED Sources of Stray Light Common stray light sources include: Diffraction Specular ghosts Grating effects from manufacturing Scatter from structures Particulate contamination Thermal self-emission Background sources Bulk material effects

FRED Effects of Stray Light Stray light = performance reduction Stray light should be accounted for during design Correcting stray light requires knowledge of the source FRED provides engineers a toolbox for stray light analysis

FRED Stray Light Tools Surface Scatter Models Lambertian Harvey-Shack ABg Phong Diffuse Black Paint Particulates (Mie) Diffuse Polynomial Diffuse Binomial Tabulated BSDF Tabulated PSD K-correlation User-scripted (BASIC)

FRED Stray Light Tools Scatter Importance Sampling Scatter rays only into regions of interest Saves time by raytracing efficiently Correctly accounts for ray directions Importance Sampling Options Angular spread about specular Angular spread about a given direction Angular spread about a given point Towards an entity Through a closed curve Through a volume

FRED Stray Light Tools Volume Scattering Stray light effects can come from bulk material volume scatter Implemented as “random walk” using a mean free scatter distance Translucent materials, suspended particulates, etc.

FRED Stray Light Tools Surface Raytrace Controls Allows specific interaction types: scatter, transmission, reflection etc. Set ray power cutoff thresholds Specify number of allowed ray splits due to scatter or specular Precise control over model tracing Applied to individual surfaces

FRED Stray Light Tools Raypaths and Stray Light Report Keeps track of ray intersection paths Sorts raypaths by scatter and specular Reports scatter/ghost level Provides information on ray count, path power, scatter/ghost surfaces Paths can be marked for sequential tracing Raypaths can be redrawn to the 3D view

FRED Stray Light Tools Diffraction Grating structures Linear XY Polynomial with aspheric terms Diffraction from apertures, edges, slits, etc. when tracing coherent rays

FRED Stray Light Tools BASIC Compiler and Scripting FRED’s fully integrated BASIC scripting language allows for custom calculations such as thermal self-emission and PST

FRED Stray Light Example Ghosting in a Double Gauss Lens 10 degree off axis angle Uncoated lenses Allow only first order paths straylight_ghostImage.frd

FRED Stray Light Example Ghosting in a Double Gauss Lens Allow all raytrace paths Irradiance distribution shows ghost image

FRED Stray Light Example Ghosting in a Double Gauss Lens Use FRED’s Stray Light Report to identify the ghost path(s) Ghost is caused by a reflection from surface 10

FRED Stray Light Example Ghosting in a Double Gauss Lens Apply an AR coating to surface 10 Ghost image power reduced by an order of magnitude!

FRED Optimization Applications What is optimization used for? Positioning geometry Controlling geometry size Modifying surface shapes Detector power transfer efficiency Field distribution, shape and size Pattern structure variation Color image analysis User-defined merit functions and variables Selection of Global and Local optimization methods

FRED Optimization Variables Default Variables Custom Variables What variables are available? Any entity property in the model can be a variable Default Variables Custom Variables Position/Orientation parameters Curvature NURB control point X,Y,Z coordinates NURB control point weights Conic constant Aspheric coefficients Lens bending Lens power Lens thickness Element volume boundary User-defined BASIC script Scripting commands give access to every parameter and function available in the GUI

FRED Optimization Metrics Custom Metrics Default Metrics What metrics are available? Custom Metrics Default Metrics Project specific requirements may necessitate user-defined custom metrics be used. RMS spot size Encircled spot radius Maximum power on surface Minimum power on surface Uniformity Centroid position Distribution fit to data

FRED Optimization Example Optimize an LED Distribution Use FRED to optimize an LED collimating lens for a uniform illuminance distribution by varying the lens surfaces.

FRED Optimization Example Optimize an LED Distribution User-defined metric driven to a minimum by the simplex Metric needs to account for both power and uniformity Metric = SD/Power Scripted metric is… BASIC Calculate Illuminance Calculate SD Calculate Power Transfer Return Metric Value

FRED Optimization Example Optimize an LED Distribution 55 LUX (lm/m ) 2 88.5 LUX (lm/m ) 2

Illumination Capabilities FRED Illumination Capabilities What are FRED’s Capabilities? CAD import/export from STEP and IGES Catalog materials and components Optimization capability Photo-realistic rendering Rayset import from file including: Photometric power units (Lumens) FCR ( FRED’s compact rayset ) Photometric analyses (Illuminance, Luminous Intensity) RAY ( ProSourceTM ) Color image analysis DAT ( ZEMAXTM, ProSourceTM) DIS ( ASAPTM ) TXT( ASCII ) Default source types Plane waves, spherical waves, Gaussian TEM00, Astigmatic Gaussian Custom source types Gaussian (Hermite, Laguerre, Laguerre Cosine, Laguerre Sine), R^n, Amplitude/Phase mask, Lambertian, Inverse Lambertian, cos^n, sin^n, Sampled IES output

FRED CAD Import/Export FRED reads and writes CAD files in STEP or IGES format All surface types are exported (exception: user-scripted) with proper trimming User-specified sampling for accuracy requirements Default raytrace control assignment on import NURB order reduction and curve simplification for tolerancing Rays can be drawn and exported in color with the model

FRED Geometry FRED has 30+ default surface and curve types Custom scripted geometries for added flexibility Entities can be referenced to ANY coordinate system for accurate and dynamic positioning Integrated component catalogs for rapid prototype development or proof of concept designs CAD interface and object tree hierarchy for logical system organization and construction Arbitrary surface trimming operations using surfaces and curves

FRED Ray Import/Export 1 2 FRED reads ray file formats RAY, DAT, DIS, TXT and writes formats FCR, TXT, RAY, DAT Creating a model with ray data can be a simple two step process: Open/Import geometry from file Create source from ray file data FRED’s advanced Ray Manipulation Utilities allows modification and filtering of rays before export Rayfile import automatically sets the power of the source according to the power contained in the rays 1 2

Custom Source Creation FRED Custom Source Creation FRED allows source customization using combinations of the following parameters: Ray Positions Spectral Range Ray Directions Spectral Weighting Angular Power Apodization Coherence Positional Power Apodization Polarization Source Power Units Digitization tools for data sheet specification Source power can be radiometric or photometric units Wavelengths can be specified using a sampled list or continuous spectral function

FRED Optimization FRED has a built in optimization engine Default variables and aberrations and user-scripted variables and aberrations Continuously expanding default optimization functionality Uniformity Optimization 55 LUX (lm/m ) 2 Position/Orientation parameters RMS spot size Encircled spot radius Curvature Maximum power on surface NURB control point X,Y,Z coordinates Minimum power on surface Uniformity NURB control point weights Centroid position Conic constant Distribution fit to data Aspheric coefficients Lens bending Lens power Lens thickness Element volume boundary 88.5 LUX (lm/m ) 2 hybrid_optimization.frd

FRED Photometric Analysis Sources can be defined in both radiometric and photometric power units Wavelength spectrum can be sampled or functionally defined Illuminance and Luminous Intensity calculations User-defined detector response functionality Color image calculations using both radiometric and photometric source definitions lawnLamp.frd

Photorealistic Rendering FRED Photorealistic Rendering FRED has the capability to render a scene photo-realistically Scene objects be applied with physical optical properties Scatter importance sampling and reverse raytracing allow for efficiency

Coherence Capabilities FRED Coherence Capabilities What are FRED’s Capabilities? General complex field propagation Birefringence Default source types Interferometry Plane waves, spherical waves, Gaussian TEM00, Astigmatic Gaussian Laser ranging Precision metrology Custom source types Fiber coupling Gaussian (Hermite, Laguerre, Laguerre Cosine, Laguerre Sine), R^n, Amplitude/Phase mask, Lambertian, Inverse Lambertian, cos^n, sin^n, Sampled Wavefront decomposition Partial coherence Field polarization Ray synthesis from arbitrary field data Spatial resampling Diffraction: Aperture, edge, slit, etc. Multi-mode beam simulation

FRED Aperture Diffraction Plane wave source diffracting from a triangular aperture

Obscuration Diffraction FRED Obscuration Diffraction Diffraction from secondary mirror struts and baffle on a Cassegrain Telescope cassegrain.frd

FRED Fiber Coupling Fiber coupling efficiency Single Mode Step Index Gaussian Mode z-position CE

Near Field Diffraction FRED Near Field Diffraction Fresnel zones – Near field diffraction structure

Polarization & Birefringence FRED Polarization & Birefringence Alignment of a ruby laser with polarization filters and birefringent materials

FRED Interferometry Fizeau homogeneity test Inhomogeneous material

FRED Partial Coherence a b c Diffractometer Degree of Coherence |12| Pinhole spacing (mm) a b c A P1 P2 L1 L2 s1 L0 s0 F R 2o 21