Image:Zonenplatte Cosinus.png

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[edit] Description

Description
Deutsch: Frenelsche Zonenplatte mit Sinusförmiger Transparenzfunktion. Programmcode zur Berechnung siehe unten.
English: Frenel's zone plate with sinusoidal transparency. For calculation code see below.
Source

Home brewed picture
Date

created 19. Aug. 2005
Author

Georg Wiora (Dr. Schorsch)
Permission
(Reusing this image)

CC-BY-SA 2.5, 2.0, 1.0 and GFDL by the Author

[edit] Licensing

Some rights reserved
Creative Commons Attribution iconCreative Commons Share Alike icon		 This file is licensed under the Creative Commons Attribution ShareAlike license versions 2.5, 2.0, and 1.0

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I, the copyright holder of this work, have published or hereby publish it under the following license:
GNU head Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation license, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation license".

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[edit] How To

The 8-bit intensity values I of this image were computed by the following formula:

I(r) = COS(\frac{r^2}{5120})\cdot 127 + 128

where r is the distance to the image center in pixels.

The image has been computed with IDL (Interactive Data Language from www.rsinc.com ). The source code is provided here. Copy it into a file named "Zoneplatecosinus.pro" and execute it with IDL.

 PRO ZONEPLATECOSINUS
   ; Pixel size of the image
   siz=1000
 
   ; Coordinate array
   xc = LINDGEN(siz,siz)
   yc = xc / siz
   xc = TEMPORARY(xc) MOD siz
 
   ; Distances to center of array
   d = SQRT((FLOAT(xc)-siz/2.)^2+(FLOAT(yc)-siz/2.)^2)
   ; The image of the zone-plate
   zone = COS(d^2/5120)
 
   WINDOW,XSIZE=siz,YSIZE=siz
   ; Display it
   TVSCL,zone
 
   ; Save as PNG
   write_png,'zonenplatte2.png',BYTSCL(zone)
 END

Historique du fichier

Cliquer sur une date et une heure pour voir le fichier tel qu’il était à ce moment-là

Date et heureDimensionsUtilisateurCommentaire
actuel17 mai 2008 à 07:291 000×1 000 (260 Kio)Falcorian (pngout compression.)
19 août 2005 à 16:111 000×1 000 (296 Kio)Xorx ({{Information| |Description = Frenel's zone plate with sinusoidal transparency. |Source = Home brewed picture |Date = created 19. Aug. 2005 |Author = Georg Wiora ~~~ |Permission = Put under the GFDL by the Author. |other_versions = - }} {{GFDL-self}})

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