Float By Stop Size is one way to define the aperture of your system. It means that the system aperture is determined by the semi-diameter of the stop surface (regardlesss of its location), which is set by the user as the Clear Semi-Diameter value in the Lens Data Editor. This could be quite handy when dealing with a system where the stop surface is a real aperture with a pre-determined size located somewhere within the system. Since the entrance pupil diameter, image space F/#, object space NA, and aperture stop radius are all related, any one of these are equally valid ways to define the aperture of the system.

I've always thought that Float-By-Stop was an awkward and fairly meaningless name. Zemaxers, any chance of just renaming it to 'Physical Size of Stop Surface' or something that actually gives the user a clue what it is, without reading the manual?

Hi,

I am new to Zemax, and really struggle with the explanations that further need to be explained for example: What is the semi-diameter of the stop surface? It could be useful to add some drawing of the lenses. 

Meaning of semi-diameter of stop surface is the half the diameter of the stop surface (in general any surface). Here diameter refer to Clear aperture (or physical diameter) of that surface.

In below screenshot I have assumed the lens 1st surface as the stop. In general it can anywhere in the system, But same analogy will be applied.

Meaning of semi-diameter of stop surface is the half the diameter of the stop surface (in general any surface). Here diameter refer to Clear aperture (or physical diameter) of that surface.

In below screenshot I have assumed the lens 1st surface as the stop. In general it can anywhere in the system, But same analogy will be applied.

 

Hi, please, In trying to Propagate laser beam with a defined diameter, what aperture do you suggest i use? I wanted Using the float by stop size but i figured it will reduce the beam passing through since the aim will be to have an aperture that will allow all of the laser beam pass through.

Hi,

My usual practice to work with laser beam design is to set the aperture as object space cone angle, and set the aperture value same as laser half angle divergence (please note: in this case you need to look which divergence axis you want to take for the design, major axis or minor axis).

Flot by stop size should also work, just calculate the beam width at a particular distance (with which you want to work with) and enter the semidia of the laser beam to “semidiameter” column of stop surface.

Thanks.