If we increase the distance of convex lens, whether spot size dicrease or increase?
It kind of depends on what your specific setup is. Could you provide some details about it?
I see. I assume that the beam is more or less collimated before the convex lens, and is focused after going through the lens. I also assume you are doing the knife-edge method because you want to determine the light spot size at a certain position. Let's consider two scenarios:
1) These is little geometric aberration before the beam goes through the lens:
The beam then focuses at the focal plane of the convex lens. The spot size is smallest at the convex lens focal plane. If the position you are at is between the convex lens and its focal plane, increasing the distance from the convex lens will lead to a smaller spot size. If the position you are at is beyond the convex lens focal plane, increasing the distance from the convex lens will give you a larger spot size.
2) If there are significant geometric aberrations in the beam before it goes through the convex lens:
The beam roughly focuses at the convex lens focal plane. If the position you are at is far from the convex lens focal plane, 1) still holds. However, if you are near the convex lens focal plane (i.e., only a few depths of field away), the light spot can become weird (e.g., asymmetrical) and the spot size not well-defined.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials
- Inorganic Materials
- Metals
- Alloys
- Steel