Skip to main content
This is an image of a ray going through a lens in ZEMAX.  The model is sequential, and so obviously the ray cannot do what is pictured.  Many of the adjacent rays have the same problem, but most of the rays in the model do not show this problem --- this is a ray from near the edge of the image.

 

The rays are being drawn to some dummy surfaces. In your Lens Data Editor, go to the Draw properties for the non-optical surfaces and check “Skip Rays To This Surface:”

 

This seems like a very good answer.  There are coordinate breaks both before and after that lens, and those surfaces did not have “Skip Rays To This Surface”.  However, doing this suggestion did not solve the problem.  I was curious to note that checking “Skip Rays To This Surface” for the actual top and bottom surfaces of the lens changed the ray’s trajectory inside the lens, but did not affect the ray’s trajectory either before or after the lens --- in other words this erroneous drawing did not affect the final destination of the ray at the detector, several lenses further on.  I’m inclined to believe that this is just a glitch in the drawing and not a glitch in the optimization calculation.

@Antony.Stark 

 

Can you fletch the rays in your 3D Layout and show us that same screenshot?

Although we cannot exclude a glitch, I’ve never come across such behavior so far.

Take care,

 

David

Here it is, with fletching.  The glitched part of the ray is going upwards and then just stops.  There is no surface defined where it stops.  BTW, I have been working on this design in several versions of ZEMAX going back to versions from before the pandemic, and this problem is present in all of them, it’s not a new problem.

 

@Antony.Stark

 

Could you uncheck Skips Rays To This Surface and Do Not Draw This Surface for all surfaces and give us the screenshot again? Sorry I should have said it before but seeing those rays and surfaces might help understand the behavior of those rays.

Have you tried using the Analyze..Rays & Spots..Single Ray Trace to get more details about the glitched ray?

Take care,

 

David

OK, you’ve solved it!   The problem was, as shown below, is that there is a dummy surface after the second lens.  That surface is a flat plane, and it has no material (and so doesn’t do anything to the optics), but there were some variables that allowed it to tilt.  There were constraints on it in the Merit Function that should have prevented it from tilting too much (it’s supposed to represent the position of a local image of the source), but these did not work properly and this “null” surface tilted enough so that part of it was actually before the lens that precedes it in the sequential lens list.  Since the surface had “Do Not Draw This Surface” checked, this error was not apparent. ZEMAX did the best it could with it, running the ray backwards up to that surface, but since the surface was a dummy surface with no effect on the optics the ray then continued downward from the lens as it should. 

In orange is a dummy surface that was supposed to be below the lens, but with insufficient constraints on its tilt part of the dummy surface was actually before the lens that was supposed to precede it.  This did not effect the convergence of the model, since the dummy surface had no material, but the ray trace did its best to hit every surface.

 

Reply


Community Posting GuidelinesCookie settings