JenTrace 1.0.0

Python library for optical ray tracing

JenTrace

Python-based ray trace library for optical design and optimization.

Description

W.T. Welford in his book titled "Aberrations of the symmetrical optical systems"(Academic Press Inc, 1974) descrive a simple sequential algorithm to trace rays through spherical surfaces. This algorithm, called from now on "trace", is implemented in a python function and will be the core of this module. Additional concepts such as ray, surface, point source and optical system have been defined in classes which are going to be used in the optical designs. The data stored in the classes is intendet to be transparent to the user, in case he or she want to display the information or the results in a particular way. Nevertheless, a few basic functions for visualization and optimization are provided to the user, which are based on the modules matplotlib and scipy respectively. This project is oriented to entusiast and students with interest in optical design and programming.

Getting Started

Dependencies

python >= 3.7
numpy >= 1.18.1
matplotlib >= 3.1.3
scipy >= 1.4.1

Installing

Install the module using the following pip command (for Windows users, you can use the Powershell promp of Anaconda),

pip install -i https://pypi.org/ JenTrace

In case you were not able to download the module from PyPi. One option to use the JenTrace module consist in downloading the "src" folder in your computer and adding the path manually. Use the command sys.path.append with the path where you save the "src" folder.

import sys
sys.path.append("C:\\...yourPath...\\src")

Example

Check the following example, to see the JenTrace capabilites: https://github.com/dlvasquezp/JenTrace/blob/main/examples/quickStart.ipynb

For Developers

The module JenTrace is based on two concepts:

1.1) ray: A ray is a list of elements describing the ray position, direction and wavelength.

ray0 = [[X,Y,Z], [L,M,N],wvln]
[X,Y,Z]: position in mm
[L,M,N]: direction cosines
wvln:    wavelength in nm

1.2) surface: A surface is a list of elements describing the surface distance, curvature, refraction index (material) and surface type.

surf0 = [d,C,n,'type']
d: distance to the next surface in mm
C: curvature (1/r) in mm
n: refraction index (float) or material name (string)
type: (optional) surface type e.g. 'paraxial','standard','grin' 

From this two concepts the following classes are created:

2.1) RaySource: is a class which contains collection of rays (lists) and a set of methods to add modify or delete rays.

Two sub-classes of ray source are supported:

2.1.1)PointSource: all the rays share the same origin ([X,Y,Z]) but differ in the direction.

2.1.2)InfinitySource: all the raysshare the same direction ([L,M,N]) but differ in the origin.

In the Point/Infinity source, the ray position (index) has a particular roll. The first 5 rays (0 to 4) are named "essential" because they are necessary for any optical design characterization.

index       Name when on axis           Name when off axis
0           optical axis                chief ray
1           y upper marginal ray        y upper coma ray     (y:meridional)
2           y lower marginal ray        y lower coma ray
3           x positive marginal ray     x positive coma ray  (x:sagital)
4           x negative marginal ray     x negative coma ray       
5 or >      screw ray                   screw ray  

ray#index
ray0: (or chief ray)is directed to the aperture stop (AP) center
ray1: (or marginal ray)is directed to the meridional upper AP boundary
ray2: is directed to the meridional AP lower boundary
ray3: is directed to the sagital positive AP boundary
ray4: is directed to the sagital negative AP boundary
ray5,6,7...: rays directed in any direction to the AP

2.2) opt_sys: a optical system is a collection of surfaces (lists).

#           Nmae              
0           object
1           surface
...         surface  
N           image (last surface) 

Finally with a ray source and an optical system a ray trace can be done,

3.1) trace: A trace is a function where the rays are propagated through the surfaces. It is based on propagation Welford's method. It returns a matrix called RayTrace with the propagation values.

For sake of simplicity an optical design is define, which will find automatically the values need for the design evaluation:

4.1) opt_dsg: A optical design accepts a ray source and a optical system to to perform a ray trace. An important attribute of the optical design is the position and size of the AP. With this information the optical system can calculate the rays direction and optical properties of the system.

          Each optical design has the following attributes:
          
          Arguments passed by the user:
          usrSrc: user defined point/infinity source
          optSys: optical system
          aprRad: aperture stop radius 
          aprInd: aperture stop index
          
          Attributes created when instantiated:
          dsgPtoSrc: point source at position [0,0,0] 
          dsgInfSrc: source at infinity with direction [0,0,1]
          
          RayTrace calculated when instantiated:
          raySrcTrace -> ray source and optical system
          dsgPtoTrace -> point source and optical system
          dsgInfTrace -> source at infinity and optical system
          
          Merit functions used in the process:
          essential_LMN: calculate the direction LMN of the point source
                         "essential" rays. It returns the difference (error) 
                         between the ray position and the aperture coordinate.
          essential_XYZ: calculate the position XYZ of a source at infiniy
                         "essential" rays. It returns the difference (error) 
                         between the ray position and the aperture coordinate.

Final comments:

"Readability counts"

Class: CapWords

Function: all lower case + underscore

Variables: CapWords + short name

Contributors

David L. Vasquez

Acknowledgements

Prof. Yobani Mejia from Universidad Nacional de Colombia

Prof. Herbert Gross from Friedrich-Schiller-Universität Jena

The Leibniz Institute of Photonic Technology (Leibniz-IPHT) and the great city of Jena, Germany.