Now, it is time to look at the partially coherent results. First, let us try a small Alpha value (i.e. 0.0025). We know that for small Alpha values, the resulting Gamma function is narrow and, as such, the results are mostly incoherent. Change “Data Type” to Partially Coherent Image (Mostly Incoherent Method) and set “Alpha” to 0.0025. Observe that the resulting image looks very much like the incoherent one we recently saw. The narrower the Gamma function, the more incoherent the resulting image will appear to be:

Now, let us try a large Alpha value (i.e. 0.1). We know that for large Alpha values, the resulting Gamma function is broad. As a result, the results are mostly coherent. Change “Data Type” to Partially Coherent Image (Mostly Coherent Method) and set “Alpha” to 0.1. Notice that, not surprisingly, the resulting image looks very much like the coherent result we saw previously. The broader the Gamma function, the more coherent the resulting image will appear to be:

Now, try an Alpha value that is neither small nor large (i.e. 0.01). First, let’s take a look at the Gamma function. Change “Data Type” to Partially Coherent Test:  Gamma and set “Alpha” to 0.01. Observe that the resulting Gamma function is narrower than the function for an Alpha value of 0.1 but more broad than that for an Alpha of 0.0025, as expected:

From the display, it is clear that the Gamma function covers more than 20% of our image, so we will still use the Mostly Coherent method here. Change “Data Type” to Partially Coherent Image (Mostly Coherent Method). The resulting image clearly shows spatial interference effects, but, as expected, these effects are not as pronounced as they are for a broader Gamma function as we just saw (i.e. Alpha = 0.1):

The following animation shows the gradual transition from incoherent to partially coherent to coherent Diffraction Image Analysis for our three bar source: