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Deutsch: Numerisch berechnete Intensitätsverteilung hinter einem Mehrfachspalt dargestellt als Hitzefeld. Nicht berücksichtigt wurde die Freiraumdämpfung. Deutlich zu erkennen die Hauptmaximas und dazu schwach die Nebenmaximas. Hier wurde zur weiteren Veranschaulichung kein endliches Gitter sondern eine Wellenfront mit begrenzter Weite eingezeichnet. In der Nähe des Gitter treten Alias-Effekte auf, die wegen der begrenzten Auflösung entstehen.
Date
Source Own work
Author Miessen
PNG development
InfoField
 
This diagram was created with MATLAB.
 config.ini 
;
; Some nice values
;

dim_x = 4000
dim_y = 2700
free_space_loss = 0
; gap width as factor to grating_distance
gap_width = 0.2
grating_count = 10
; grating_distance approx 2000 nm
; scaling_meter_per_px * 3/gap_width
grating_distance = 2250.e-9
offset_x = 600
; igonre...; 30 px per wave = 700.e-9 / 30px
; calculate near field / far field
scaling_meter_per_px = 150e-9
slit_width = 0
slit_iterations = 0
; 700 nm
wave_length = 700.e-9
Source code
InfoField

diffraction_grating.m code

#!/usr/bin/octave -qf
% \usr\bin\octave

%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% Miessen 2014
%
%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  getParameters
%
%%%%%%%%%%%%%%%%%%%%%%%%%%

function setParameters(config)
  global parameters;
  
%  parameters.grating_distance = getConfigValue(config, "grating_width");
  parameters.dim_x = int32(getConfigValue(config, "dim_x"));
  parameters.dim_y = int32(getConfigValue(config, "dim_y"));
  parameters.free_space_loss = getConfigValue(config, "free_space_loss");
  parameters.gap_width = getConfigValue(config, "gap_width");
  parameters.grating_count = int32(getConfigValue(config, "grating_count"));
  parameters.grating_distance = getConfigValue(config, "grating_distance");
  parameters.offset_x = int32(getConfigValue(config, "offset_x"));
  parameters.scaling_meter_per_px = getConfigValue(config, "scaling_meter_per_px");
  parameters.wave_length = getConfigValue(config, "wave_length");
endfunction

%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  findGapPositions
%
%%%%%%%%%%%%%%%%%%%%%%%%%%

function gaps = findGapPositions(grating_distance, grating_count)
  if (grating_count < 2)
    error("grating_count too small");
  endif
  
  width = grating_distance * (double(grating_count)-1);
  gaps = [];
  for i = 0:(grating_count-1)
    gaps = [gaps (i*grating_distance-width/2)];
  endfor
endfunction

%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  gratingSignalStrength
%
%%%%%%%%%%%%%%%%%%%%%%%%%%

function amplitude = gratingSignalStrength(x, y, gaps, wave_length, free_space_loss)
% grating {gaps, sub_steps, gap_width }
% free_space_loss not implemented

  % calculate distances
  distances = [];
  for gap_pos = gaps
    distances = [ distances sqrt((y-gap_pos)^2 + x^2) ];
  endfor
  
  % calculate amplitudes
  c_amps = [];
  base_distance = sqrt(x^2 + y^2);
  
  for d = distances
%    delay = d - base_distance;
%    phase = 2. * pi * delay/wave_length;

    % amplitude phasor = c_amp
    residual = rem(d, wave_length);
    phase = 2. * pi * residual/wave_length;
    c_amp = complex(cos(phase), sin(phase));
    c_amp = c_amp / d; % free_space_loss ?? check - Integrate a slit!

    c_amps = [c_amps c_amp];
  endfor
  
  % calculate amplitude
  amplitude = abs(sum(c_amps))/length(gaps);

  % eliminate free_space_loss
  max_sum = sum(abs(c_amps))/length(gaps);
  amplitude = amplitude/max_sum;
  
endfunction

%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  slitSignalStrength
%
%%%%%%%%%%%%%%%%%%%%%%%%%%

function amplitude = slitSignalStrength(x, y, sub_steps, gap_width, wave_length, free_space_loss)

endfunction

%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  calculateDiffraction
%
%%%%%%%%%%%%%%%%%%%%%%%%%%

function amplitudes = calculateDiffraction(gaps )
  printf("Calculate Diffraction\n");


  global parameters;
  
  % Read globals
  dim_y = parameters.dim_y;
  dim_x = parameters.dim_x;
  scaling_meter_per_px = parameters.scaling_meter_per_px;
  offset_x = parameters.offset_x;
  wave_length = parameters.wave_length;
  free_space_loss = parameters.free_space_loss;

  % Calculate dimensions
  x_max = double(dim_x - offset_x - 1) * scaling_meter_per_px;
  y_width = double(dim_y - 1) * scaling_meter_per_px;
  y_max = y_width / 2.;
  y_min = -1. * y_max;
  
  % Initialize
  amplitudes = zeros(dim_y, dim_x - offset_x);
  
  
  for amp_pos_x = int32(1:(dim_x - offset_x))
    printf("%3d%%", 100 * amp_pos_x/(dim_x - offset_x));
    for amp_pos_y = int32(1:1:dim_y)
      x = double(amp_pos_x) * scaling_meter_per_px;
      y = y_min + double(amp_pos_y) * scaling_meter_per_px;
      
      amp = gratingSignalStrength(x, y, gaps, wave_length, free_space_loss );
      amplitudes(amp_pos_y, amp_pos_x) = amp; % row = y / column = x
    endfor
    printf("\b\b\b\b");
  endfor
  printf("Finished calculateDiffraction\n");
  
  

endfunction

%%%%%%%%%%%%%%%%%%%%
%
%  generateGrating
%
%%%%%%%%%%%%%%%%%%%%

function rgb = generateGrating(rgb)
  printf("Generate Grating\n");
  global parameters;
  
  dim_y = parameters.dim_y;
  grating_count = parameters.grating_count;
  grating_distance = parameters.grating_distance;
  gap_width = parameters.gap_width;
  offset_x = parameters.offset_x;
  scaling_meter_per_px = parameters.scaling_meter_per_px;

%//  gray = zeros(dim_y, offset_x);

  y_width = double(dim_y - 1) * scaling_meter_per_px;
  y_max = y_width / 2.;
  
  % even or odd 
  if ( round(rem(grating_count, 2)) != 1. )
    even_factor = 0.5; % grating_distance/2.;
  else
    even_factor = 0.;
  endif
  
  
  for y_px = int32(1:dim_y)
    y = double(y_px) * scaling_meter_per_px;
    stepper = y / grating_distance; % normalize
    sub_stepper = stepper + even_factor - round(stepper);
    % sub_stepper = rem(stepper,1);
    % stepper
    % odd: -0.5..+0.5
    % even: 0.0..1.0
    % Nachkommazahlen
  
  % sub_stepper +/- 0.5 * grating_distance around gap
    for x_px = offset_x-int32(double(offset_x)/40.):offset_x
      if(abs(sub_stepper) <= gap_width)
        rgb(y_px, x_px, :) = [0., 0., 0.];
      else
        rgb(y_px, x_px, :) = [0.8, 0.8, 0.8];
      endif
    endfor
  endfor
   
endfunction


%%%%%%%%%%%%%%%%%%%
%
%  generateLaser
%
%%%%%%%%%%%%%%%%%%%

function amplitudes = generateLaser()
  printf("Generate Laser\n");
  global parameters;

  dim_y = parameters.dim_y;
  grating_count = parameters.grating_count;
  grating_distance = parameters.grating_distance;
  offset_x = parameters.offset_x;
  scaling_meter_per_px = parameters.scaling_meter_per_px;
  
  y_width = double(dim_y - 1) * scaling_meter_per_px;
  y_min = -1. * y_width / 2.; 
  
  laser_width = grating_distance * double(grating_count)
  
  amplitudes = [];
 
  for y_px = int32(1:dim_y)
    y = y_min + double(y_px) * scaling_meter_per_px;
    
    if (abs(y) <= laser_width / 2.) 
      amplitudes = [amplitudes; ones(1,offset_x)];
    else
      amplitudes = [amplitudes; zeros(1,offset_x)];
    endif
  endfor
  
endfunction

%%%%%%%%%%%%%
%           %
%  M A I N  %
%           %
%%%%%%%%%%%%%

global parameters

begin_cputime = cputime();


printf("Including CSV library\n");
echo_csv_lib = 0;
source ("./lib/csv_lib.m");
printf("Including config library\n");
global echo_config_lib = 0;
source ("./lib/load_config_lib.m");

printf("Starting\n");


arg_list = argv ();

if (rows(arg_list) != 2);
  printf("wrong parameters, config file and output file needed.\n");
  exit();
endif

config_filename = arg_list{1};
output_filename = arg_list{2};

config = loadConfig(config_filename);

% config

setParameters(config);

gaps = findGapPositions(parameters.grating_distance, parameters.grating_count);

gaps

% dim
% step
% wavelength
%

printf("Dimensions:\n");

% Debug
%x_width = parameters.scaling_meter_per_px * double(parameters.dim_x)
%y_width = parameters.scaling_meter_per_px * double(parameters.dim_y)
%amp = gratingSignalStrength(x_width, 0, gaps, parameters.wave_length, parameters.free_space_loss );
%amp

diffractionMap = calculateDiffraction(gaps);
max(max(diffractionMap))
diffractionPowerMap = diffractionMap.^2;

laserMap = generateLaser();
laserPowerMap = laserMap.^2;


map = jet();

diffractionInd = gray2ind(diffractionPowerMap);
diffractionRgb = ind2rgb (diffractionInd, map);

laserInd = gray2ind(laserPowerMap);
laserRgb = ind2rgb (laserInd, map);



offsetRgb = generateGrating(laserRgb);

finalRgb = [offsetRgb diffractionRgb];
%finalRgb = [offsetRgb]; % debug



imwrite(finalRgb, output_filename, "png");


printf("Total cpu time: %f seconds\n", cputime()-begin_cputime);
printf("Finished\n");

Lib/csv_lib.m code

%
% GNU Octave library to write results to a csv file
%

1; % not a function file


%
% Add header to CSV file
%

function csvFile = addCsvFileHeader(csvFile, header)
  if (isfield(csvFile, "headerList") == true)
    csvFile.headerList = [csvFile.headerList; header];
  else
    csvFile.headerList = [header];
  endif
endfunction

%
% Add record to a structure CsvLine based on existing header
%

function csvLine = addCsvLineRecord(csvLine, header, value)

  csvLine.(header) = value; 

endfunction

%
% Close CSV file
%

function csvFile = closeCsvFile(csvFile)

  fclose(csvFile.fid);

  csvFile.isOpened = false;
endfunction

%
% Create a CSV line for this file
%

function csvLine = createCsvFileLine(csvFile)

  csvLine.headerList = csvFile.headerList;
  for header = csvLine.headerList'
    csvLine.(strtrim(header')) = "";
  endfor

endfunction

%
% Output values of a csv line
%

function csvLine = printCsvLine(csvLine)

  csvLine

endfunction

%
% Open CSV file
%

function csvFile = openCsvFile(filename)
  csvFile.filename = filename;
  
  % test if already exists
  
  csvFile.fid = fopen(csvFile.filename, "w");

  csvFile.isOpened = true;

endfunction

%
%
%

function csvLine = writeCsvFileHeader(csvFile)
  line = "";
  for header = csvFile.headerList'
    line = [line, strtrim(header')];
    line = [line, ","];
  endfor

  line = substr(line, 1, length(line)-1);
  fprintf(csvFile.fid, "%s\r\n", line);

endfunction

%
%
%

function csvLine = writeCsvLine(csvFile, csvLine)
  line = "";
  for header = csvLine.headerList'
    line = [line, csvLine.(strtrim(header'))];
    line = [line, ","];  
  endfor
  line = substr(line, 1, length(line)-1); % remove last comma
  fprintf(csvFile.fid, "%s\r\n", line);
endfunction

Lib/load_config_lib.m code

%
% GNU Octave library to load values from a config file
%

if(exist("echo_config_lib", "var") == 0)
  global echo_config_lib = 1;
endif



%
%
%

function value = getConfigValue(config, var_name)
  if (isfield(config, var_name) == false)
    printf("Error: \"%s\" missing in config file\n", var_name); 
    exit();
  endif
  [value, success] = str2num(config.(var_name));
  if(success != true)
    printf("Error: Converting \"%s\" failed!\n", var_name); 
    exit();
  endif
endfunction


%
%
%

function value = getConfigInt32(config, var_name)
  if (isfield(config, var_name) == false)
    printf("Error: \"%s\" missing in config file\n", var_name); 
    exit();
  endif
  [value, success] = str2double(config.(var_name));
  if(success != true)
    printf("Error: Converting \"%s\" failed!\n", var_name); 
    exit();
  endif
endfunction


%
%
%

function value = getConfigString(config, var_name)
  if (isfield(config, var_name) == false)
    printf("Error: \"%s\" missing in config file\n", var_name); 
    exit();
  endif
  value = config.(var_name);
endfunction


%
%
%

function arrayKeyValuePair = loadConfig(filename)
  % open file
  % while has next line
  % skip if blank
  % skip if comment
  % add key value pair to array
  
  global echo_config_lib;
  
  file = fopen (filename, "r");
  line = fgetl(file);
  lineNum = 1;
  while (ischar(line));
    if (echo_config_lib != 0)
      printf("Line %i: %s\n",lineNum, line);
    endif
    if (strcmp(line, "") == 0);
      if (strcmp(substr(line,1,1), ";") == 0);
        if(length(findstr(line, "="))== 0)
          printf("Error: Invalid line!\n");
          exit();
        endif
        key = substr(line, 1, findstr(line, "=")(1)-1);
        key = strtrim(key);
        value = substr(line
            , findstr(line, "=")(1)+1
            , length(line)-findstr(line, "=")(1) );
        value = strtrim(value);
        printf("key = %s\n", key);
        printf("value = %s\n", value);
        if(strcmp(key, "") != 0)
          printf("Error: Invalid key!\n");
          exit();
        endif
        if(isfield("arrayKeyValuePair", "key") != 0)
          printf("Error: Duplicate key!\n");
          exit();
        endif
      arrayKeyValuePair.(key) = value;
      else
        if (echo_config_lib != 0);
          printf("Comment\n");
        endif
      endif      
    else
      if (echo_config_lib != 0);
        printf("Blank line\n");
      endif
    endif
    line = fgetl(file);
    lineNum += 1;
  endwhile

  fclose(file);
endfunction



% INI format
% no white space at the beginning of a line
% empty lines allowed
% comment lines start with a semicolon
% key an value are seperated by a "="
% ascending white spaces are trimed from key
% prepending and ascending white spaces are trimed from values
% in case of duplicate values the first is valid
% crlf prefered, see RFC
%

Licensing

I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

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15 March 2014

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Date/TimeThumbnailDimensionsUserComment
current19:45, 26 September 2016Thumbnail for version as of 19:45, 26 September 20163,600 × 2,700 (278 KB)CmdrjamesonCompressed with pngout. Reduced by 100kB (26% decrease).
09:36, 19 April 2014Thumbnail for version as of 09:36, 19 April 20143,600 × 2,700 (378 KB)Miessenfound a bug
14:58, 13 April 2014Thumbnail for version as of 14:58, 13 April 20144,000 × 2,700 (393 KB)Miessensuper fine resolution to avoid aliasing
09:27, 28 March 2014Thumbnail for version as of 09:27, 28 March 20141,100 × 900 (64 KB)Miessenfinal version
17:03, 15 March 2014Thumbnail for version as of 17:03, 15 March 2014450 × 450 (22 KB)MiessenUser created page with UploadWizard

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