In the System Explorer, choose the pupil diameter as the aperture type, enter 1 for the aperture value and select the afocal mode, as the optical system will not form an image on the image side.

When the "afocal" mode is selected, the evaluation of the image side will be done in angular units.

Similarly, the wavelength is set to monochromatic wavelength of 0.555 µm.

Choose” Afocal Mode Units” in Units settings as showed below.

In this example, we choose radians.

Set the stop surface as pinhole in field data editor and set the thickness of the first surface as 300mm, which is the distance between the pinhole and the image plane as showed below.

The radius of the image of a point in the image plane is the half-angle multiplied by the thickness. We need to think about the radius of the diffracted beam and the radius of the geometrical optical image.

Therefore, we use the merit function editor to define it, as shown below.

1. According to diffraction theory, the energy of the Airy disk is 83.8% of the incident energy. Therefore, you can use the operand DENC, which defines the energy of the ring, and set the "percentage" to 0.838 to obtain the corresponding radius. This value is in radians and is therefore multiplied by the "thickness" of a surface to obtain the radius of the image. 2.

The radius of the pupil can be obtained by dividing the diameter of the first face by 2 using the DMVA operand. 3.

3. The value in row 10 is the sum of the two. (Another thought is to find the larger value between 4 and 8, depending on how we think about this)

Open the Universal plot 1D from Analyze -> Universal Plot tab and click New:

Set the parameters as showed below.

X is the aperture diameter and Y is the value of merit function line 10.

Press “OK “to generate the plot below.

We can get the best resolution at pinhole diameter 0.7mm for an image distance of 300mm.

The sample file is attached for your reference.

Forgot to attach the sample file...