Imagem:Zonenplatte Cosinus.png
Origem: Wikipédia, a enciclopédia livre.
| Description |
Frenel's zone plate with sinusoidal transparency. For How-to see below. |
|---|---|
| Source |
Home brewed picture |
| Date |
created 19. Aug. 2005 |
| Author |
Georg Wiora Dr. Schorsch |
| Permission |
Put under the GFDL by the Author. |
|
The 8-bit intensity values I of this image were computed by the following formula:
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
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