An active ray is any ray whose active flag is set to True. The active flag for a ray (.active) is a member of the T_RAY structure.
In FRED, an Analysis Surface is a planar region in space in which a calculation is to be made. The Ray Specification (see ray filter below) at the bottom of its dialog box instructs the Analysis Surface which rays to use in its calculation. The Analysis Surface is NOT a surface in the sense that it does not absorb rays or flux.
The Bidirectional Scatter Distribution Function (BSDF) describes the angular distribution of scatter as a function of incident illumination. The formal definition is given by dL/dE where dL is the differential radiance of a surface and dE is the differential irradiance incident upon that surface.
Coherent (or complex) raytracing involves tracing a base ray and a group of secondary rays which represent a gaussian beamlet. These beamlets are used as a basis set from which any arbitrary complex field can be synthesized. Tracing secondary rays along with each base ray allows the amplitude and phase of a wavefront to be calculated at any point by virtue of the basic gaussian beam propagation equations for waist size w(z) and wavefront radius of curvature R(z). These gaussian beamlets must obey two rules in order for the technique to remain valid: 1) Each individual beamlet (base ray plus its secondary rays) must remain gaussian during passage through an optical system; Each beamlet must sample a surface over a region that is at worst locally quadratic. 2) If the base ray intersects a surface then all of its secondary rays must intersect the same surface.
The Color Image feature computes the XYZ Tristimulus at each pixel site of an Analysis Surface.
A curve is either a collection of points or a functional form defining a line. A curve can then be swept about an axis or extruded in a direction to make a surface.
A Custom Element is an entity type which can contain any number of surfaces and curves.
The Directional Analysis Entity is an alternative form of an Analysis Surface used to calculate Intensity on a Polar Grid. It has the shape of a sphere and is divided into equal angle increments.
An Embedded Script is a script which is incorporated with and remains a permanent part of a FRED document. Embedded Scripts have their own folder in the Tree View.
The term "Energy" calculation is used to refer to a general class of Analysis functions including Irradiance, Intensity on a Polar Grid, Color Image, Scalar Wave Field, and Vector Wave Field.
FRED Compact Rays. This acronym refers to a compact, binary ray file format read by the Imported Source type.
A standard file format used to store the results of "Energy" calculations. This file format has an extensive header containing specific information
FRED Ray Buffer Serialization. This is a binary file type containing all relevant ray data and is required for saving or reading coherent and/or polarized rays. This file type can be read only from the Ray Manipulation Utility or script commands.
All data, i.e. sources, materials, coatings, geometry, ray trace controls, etc. entered into FRED is stored in a document(s).
The Gluing feature in FRED is meant to conveniently model the cementing of two optical surfaces as is commonly done with doublet and triplet lenses as well as with lightpipes. Use of this feature requires that the two optical surfaces glued together be separated by some finite distance. The Gluing feature is implemented automatically during import of lens from CodeV, OSLO and Zemax prescriptions when the "Create edges and bevels on lens elements" option is checked on the Import Optical dialog.
This algorithm searched the FRED geometry nodes starting with a parent node and then working down through the children, grandchildren, etc. until the all progeny nodes have been searched. At each node (parent, child, grandchild, etc.), the algorithm first checks to see if the node is traceable. If the node is not traceable, then skips that node and all of its children and grandchildren. If the node is traceable, then it checks to see if the ray intersects the bounding box for that node. If the ray intersects the bounding box, then the algorithm checks to see if the node is a surface. If the node is a surface, then the algorithm checks to see if the ray intersects the surface. If the node is not a surface, and it has child nodes then it systematically follows the same process for the child nodes. This process continues until all of the nodes under a parent node have been checked. Then the algorithm moves on to the next parent node. After the algorithm has determined all the surfaces that the ray intersects, the closest surface is chosen as the next surface intersection. The process then repeats. It is possible to have a traceable surface node that is a child of a non-traceable parent node.
Intensity is a radiometric unit for power per stradian. The radiometric unit for intensity is Watts/sr. Its photometric equivalent is Luminous intensity measured in lumens/sr or candela.
Irradiance is a radiometric unit for power per unit area. The radiometric unit for irradiance is Watts/meter2. Its photometric equivalent is Illuminance measured in lumens/meter2 or lux.
The Lens entity in FRED is a construct used to denote a specific geometric type. The Lens is parameterized from a single dialog box and has a specific icon 1) The two lens surfaces must share a common axis, and 2) all surfaces of a Lens must be immersed in the same material.
When these restrictions are not compatible with model requirements, the Lens can be converted to a Custom Element. Users can create their own custom lenses or select specific lenses from six vendor catalogs.
This algorithm systematically checks every traceable surface node to determine if the ray interests the bounding surface. If the ray intersects the bounding surface, then the algorithm checks to see if the ray intersects the surface. After the algorithm has determined all the surfaces that the ray intersects, the closest surface is chosen as the next surface intersection. The process then repeats.
This algorithm does not consider non-surface nodes. It is possible to have a traceable surface node that is a child of a non-traceable parent node.
A live ray is a valid ray. Allocation of rays to multiple independent CPUs and subsequent splitting/scattering ray creation leads to certain ray numbers being invalid (see Multi-threaded Raytracing).
The Mirror entity in FRED is a construct used to denote a specific geometric type. The Mirror is parameterized from a single dialog box and has a specific icon
Every entry in the Tree View data structure has a node with an icon and a name. There is a hierarchical structure to the nodes. If a node has child nodes, it can be expanded or collapsed by left mouse clicking on the + or - symbolsor by double left mouse clicking on the node name to toggle back and forth.
Power is defined as energy per unit time. The radiometric unit of power is Watts. The photometric equivalent is lumens.
The Prism entity in FRED is a construct used to denote a specific geometric type. The Prism is parameterized from a single dialog box and has a specific icon
Power Spectral Density (PSD) can be defined as surface roughness power per unit spatial frequency and is generally associated with clean, smooth surfaces. Fourier analysis and random signal theory relate surface profile measurements to PSD.
Point Source Transmittance (PST) is an industry-accepted metric for characterizing and reporting the stray light performance of an optical system. This normalized quantity is defined as irradiance at the image plane divided by irradiance at the system entrance aperture.
Ray Filter (Ray Specification) Specific rays can be selected from the ray set based on many criteria including their source, their location, coherence, etc. For example, the Best Focus command has a ray filter for selecting the subset of rays used to find the best focus. Editing, inserting, or appending a record to the ray filter will bring up the Ray Selection Criterion dialog.
The currently created set of rays in the FRED ray buffer. FRED creates rays (the rayset) from defined sources if one of the following commands are issued by the user: Create All Source Rays, Trace and Render, Trace All Sources, and Advanced Trace. Defining a source does not create rays. The rayset can be deleted using the Delete Existing Rays command. Note, single ray traces have their own separate buffer and are not part of the rayset.
Root mean sum.
Secondary rays are additional rays associated with each base ray which describe the propagation of the base ray as a Gaussian beamlet. Each base ray has eight (8) secondary rays; four waist rays and four divergence rays. Waist rays are initially created and traced parallel to the base ray at a distance 0 equal to the e-//2 energy half-width. The divergence rays are initially created coincident with the base ray position at an angle defined by the far-field divergence formula for a Gaussian beam; tan()=/0.
A steradian [sr] is the solid angle subtended by 1/4p of the area of a sphere as viewed from the center of the sphere. A hemisphere subtends 2p sr and a sphere subtends 4p sr.
A structure is a Basic construct which allows access to a collection of attributes called members. FRED's scripting language uses numerous structures to access and manipulate document data.
A subassembly is a collection of elements and/or custom elements in a FRED document. Note that surfaces and curves cannot be directly entered into a subassembly.
Only traceable objects are considered when rays are created and/or traced. Sources, parent nodes, element and custom element nodes, and surfaces by default are marked as traceable when they are created. Any source or geometry node can be marked as untraceable via the right mouse click pop-up menu in the Tree View. Node traceability can be toggled by right mouse clicking on the node and selecting "Traceable" from the list menu. A node is not traceable when its icon is grayed out and is marked with a red "X"
A count of the traceable and not traceable rays is available in the Ray Status output.
The Object Tree View is one of the two document views available in FRED and is shown on the left of the main FRED document window. This view is a hierarchical data structure representing the optical model described in FRED.
Visualization Window (3D View) The Visualization Window is one of the two document views available in FRED and is the main 3D view of the FRED document. The other view is the Tree View.
|
