diff --git a/doc/source/examples/fresnel_diffraction_example.rst b/doc/source/examples/fresnel_diffraction_example.rst
new file mode 100644
index 0000000..173cf48
--- /dev/null
+++ b/doc/source/examples/fresnel_diffraction_example.rst
@@ -0,0 +1,19 @@
+Fresnel Diffraction From A BeamStop
+===================================
+
+We simply invert an aperture to create a beam-stop. Placing this the path of a collimated beam 
+created interesting Fresnel-diffraction effects, including a bright spot at the centre of the blocked path,
+known as the Spot of Arago.
+
+.. literalinclude:: /../../examples/fresnel_diffraction.py
+
+The model looks as follows:
+
+.. image:: ../images/inverted_aperture.png
+
+However, the seem the detail in the Fresnel diffraction pattern, you need lots of Gausslets. Turn up the
+source resolution to at least 40.
+
+.. image:: ../images/fresnel_diffraction.png
+
+.. image:: ../images/spot_of_arago.png
diff --git a/doc/source/examples/index.rst b/doc/source/examples/index.rst
index 40ec82b..fea5cbe 100644
--- a/doc/source/examples/index.rst
+++ b/doc/source/examples/index.rst
@@ -5,4 +5,5 @@ Examples
 
 .. toctree::
 
-	bessel_beam_example
\ No newline at end of file
+	bessel_beam_example
+	fresnel_diffraction_example
\ No newline at end of file
diff --git a/doc/source/images/fresnel_diffraction.png b/doc/source/images/fresnel_diffraction.png
new file mode 100644
index 0000000..3c22da5
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diff --git a/doc/source/images/inverted_aperture.png b/doc/source/images/inverted_aperture.png
new file mode 100644
index 0000000..e784799
Binary files /dev/null and b/doc/source/images/inverted_aperture.png differ
diff --git a/doc/source/images/spot_of_arago.png b/doc/source/images/spot_of_arago.png
new file mode 100644
index 0000000..3137033
Binary files /dev/null and b/doc/source/images/spot_of_arago.png differ
diff --git a/examples/aperture_demo.py b/examples/aperture_demo.py
index 83c0cdb..b9d638a 100644
--- a/examples/aperture_demo.py
+++ b/examples/aperture_demo.py
@@ -1,10 +1,6 @@
 
 
-from raypier.apertures import CircularAperture
-
-from raypier.tracer import RayTraceModel
-
-from raypier.sources import ConfocalRayFieldSource
+from raypier.api import CircularAperture, ConfocalRayFieldSource, RayTraceModel
 
 
 src = ConfocalRayFieldSource(centre=(0,0,0),
diff --git a/examples/fresnel_diffraction.py b/examples/fresnel_diffraction.py
new file mode 100644
index 0000000..7b85d5c
--- /dev/null
+++ b/examples/fresnel_diffraction.py
@@ -0,0 +1,56 @@
+
+from raypier.tracer import RayTraceModel
+from raypier.sources import HexagonalRayFieldSource, ConfocalRayFieldSource
+from raypier.lenses import PlanoConvexLens
+from raypier.apertures import CircularAperture
+from raypier.fields import EFieldPlane
+from raypier.constraints import BaseConstraint
+from raypier.intensity_image import IntensityImageView
+from raypier.intensity_surface import IntensitySurface
+
+from traits.api import Range, on_trait_change
+from traitsui.api import View, Item
+
+
+aperture = CircularAperture(centre=(0,0,10), direction=(0,0,1),
+                            hole_diameter = 0.5, edge_width=0.001, invert=True)
+
+src = HexagonalRayFieldSource(resolution=10.0, direction=(0,0,1),
+                              radius=2.0,
+                              wavelength=1.0)
+
+probe = EFieldPlane(source=src,
+                    centre=(0,0,50),
+                    direction=(0,1,0),
+                    exit_pupil_offset=100.,
+                    width=2.0,
+                    height=100.0,
+                    size=100)
+
+img = IntensityImageView(field_probe=probe)
+surf = IntensitySurface(field_probe=probe)
+
+
+class FocalPlane(BaseConstraint):
+    z_pos = Range(50.0,130.0, 57.73)
+    
+    traits_view = View(Item("z_pos"))
+    
+    def __init__(self, *args, **kwds):
+        super().__init__(*args, **kwds)
+        self.on_change_z_pos()
+    
+    @on_trait_change("z_pos")
+    def on_change_z_pos(self):
+        probe.centre = (0,0,self.z_pos)
+        
+        
+
+model = RayTraceModel(sources=[src], optics=[aperture],
+                      probes=[probe], constraints=[FocalPlane()],
+                      results=[img, surf])
+
+
+
+model.configure_traits()
+
diff --git a/examples/test_hexagonal_ray_field.py b/examples/test_hexagonal_ray_field.py
index cb0cb36..7b85d5c 100644
--- a/examples/test_hexagonal_ray_field.py
+++ b/examples/test_hexagonal_ray_field.py
@@ -19,8 +19,6 @@
                               radius=2.0,
                               wavelength=1.0)
 
-src.InputRays
-
 probe = EFieldPlane(source=src,
                     centre=(0,0,50),
                     direction=(0,1,0),
diff --git a/raypier/api.py b/raypier/api.py
index 3ea904b..c7722ab 100644
--- a/raypier/api.py
+++ b/raypier/api.py
@@ -21,4 +21,6 @@
 
 from .probes import RayCapturePlace, GaussletCapturePlane
 
+from .apertures import CircularAperture, RectangularAperture
+
 from .intensity_surface import IntensitySurface