Once we had done the single slit problems we decided to work on a double slit as our object.  Below you can see the resultant image from shining our laser through a double slit where each slit was 0.54 mm and they were separated by a distance of 0.66 mm.

Image DS#1


Image DS #2                                                                        Image DS#3

Above (DS#1) you can see the characteristic double slit pattern and its plot profile in DS#2.  It is important to note the two peaks in DS#2.  Above and to the right (DS#3) you can see the FFT of our double slit created by ImageJ. (This and other images were created using a plugin from the internet, see single slit results.)  Compared to DS#4 this image is our Fraunhofer plane at a distance from the lens equal to the focal length ( 590 mm).

Image DS#4

This is the actual picture of our Fraunhofer plane.  Compared to Image DS#3 it looks as one would expect, alternating dark and light spots characteristic of double slits.  This is the FFT of our object.

Double Slit with Center Blocked at Fraunhofer Plane

Image DS#5


Image DS#6                                                                                        Image DS#7

When we tried to block the center of the light in DS#4 we found it very hard to block only that light and still get an image to show up.  You can see that the image in DS#5 appears to have the left slit totally blocked, which may be the case.  Our card blocking the light may have been too far to the left and only effectively blocked the left slit.  DS#7 doesn't show anything particularly interesting, except that the brightness of DS#7 in the middle is less than that of DS#3, showing that light in the middle of the Fraunhofer plane was blocked.

Double Slits with Sides Blocked in the Fraunhofer Plane

Image DS#8


Image DS#9                                                                                Image DS#10

In these photos you see results that you would expect from theory.  Here we blocked the arms of the Fraunhofer plane as can be seen in DS#10, where the FFT is just a small dot.  The two slits have merged into one, because the boundary information was lost due to our cards.  The plot profile in DS#9 should be compared to DS#2, and note that the two peaks seen earlier are now gone.