September 9, 2023 at 2:42 am
Yun
Subscriber

Thank you for your reply.
My lens structure and DFT monitor are already quite close, as shown in the picture in my initial questionnaire.

What I'm curious about is the idea that if you put the lens and the object closer than the focal length from the point of view of imaging the object, the vinetting will occur and the imaging will not work properly.

In the figure above, the focal length of the lens is 25 um, and the distance between the object and the lens where the planwave was incident is set to 25um.

Of course, for a 3D FDTD with a z-axis of 25 um, meshing is incredibly slow and requires a lot of resources. I don't want this.
I just wanted to know if there was another way and if I could stick it close as you said.

In general, when I thought about the imaging optical system configuration, I thought that the gap between the object and the lens should be separated by the focal length of the lens.

I circled F1 and F2 and you might think that it's okay to ignore the distance because it's the same plane wave from the Ray base

From an imaging perspective, you must keep that F1,F2 distance, but doesn't this mean that if F1,F2 changes, it will lead to Vignetting when imaging?

 

 

 

But the simulation results are strange. 

I constructed the object as 5*5 rectanglery.


After the planewave passed through the object, the image at the design focal length position of the lens was checked by farfieldexact3d.

Here are two types of pictures. the lens designed 250 um focal length

 

1. When the object and the lens are not separated by the focal length of the lens.

 

 

2. When the object and the lens are separated by the focal length of the lens.

 

 

And the important thing is that if the focal length of the lens is 250um and mag is 10, the z-axis of the x and y image that I have to look at should be 11*f (250um) and the X and Y range of the image should be 10 times larger to see the entire object.

However, both of the above types of results have not been properly represented by a 10x rate image. Why? I'm curious.