It seems like you might be asking about adjusting the brightness of the image in a microscope, not "vibreteness".

If that's the case, the part of the microscope that helps adjust the brightness is the iris diaphragm.

Here's how it works:

* Location: The iris diaphragm is usually located below the stage, and it's controlled by a lever or knob.

* Function: It's a circular opening that can be adjusted to control the amount of light that passes through the condenser and illuminates the specimen.

* Brightness control: By opening the iris diaphragm wider, you let in more light, making the image brighter. Closing it down restricts the light, making the image dimmer.

Let me know if you have any more questions about microscopes!